Also changing final drive to a more aggressive set up can also increase the amount of times you need to shift in order to reach 60mph and may alter acceleration time.
Great info, why don't manufacturers put super tall 6th gears in? If I'm on interstate and have to downshift no big deal, that's what I signed up for by driving manual.
My '95 Z28 M6 has a plenty steep 6th gear, cruising at almost idle doing 70. Obviously a Honda won't be doing that because it has no torque, maybe a better question is, why do they make so many cars that are completely gutless at lower rpm's?
years ago when i was street racing with a 79 monty with a 355 and 3 speed auto I learned a lot of this the hard way. my car was traction limited by the real wheel size i could fit and my transmission ratios were set in stone because I couldn't afford to change the ratios or add a OD. I did run a much looser converter 3500 rpm. after doing some testing and basic math I figured out a 4.56:1 ratio would be the best ratio for 1/4 mile, because it would let me run through the traps in 3rd near my TQ peak, I also learned the 4.56: would over power the traction limits of my rear tires with the suspension setup i had at the time. it took a bit of tweaking with the geometry of the 4 bars to get the pinion angle corrected and the reaction of the setup to plant the tires instead of wheel hopping and wasting energy twisting things. this was around 30 years ago. thanks for the videos that shed some new light on things
Militaristics Wow! 4.56 for 1/4 drag race!? How tall were your tires? 32+s? In the 90's I used to bracket race my old 1977 Trans Am with 4 speed in the 1/8 mile. It had a 3.73 final and 28 inch tall tires (275/60r15). It had a warmed over 400 Pontaic with Edelbrock heads. Cruising 70 mph down the highway the engine was running just over 3k. Didn't even need to down shift to pass. I can't imagine what 4.56 gears would do in that thing.
i remember running 26 or 28 in tall tires on that car with a powerband of 4500-7500 so that's why i ran the 4.56's crusing rpm wasn't a big factor as I did not drive the car for any distance and couldn't afford a gear vendors OD unit.
I've tried to explain this subject to some of my knucklehead friends who think that the taller (numerically) the gear, the faster you'll go in a quarter mile. Yes, to a certain extent, but the elapsed times, and more so, MPH, will eventually drop off. I know this because I experienced it in my own racing career. This video explains very well what happens, so I'll be sending this link to some friends. But, alas, they probably still won't get it.
Thank you for the great explanation! I am doing a rear end swap on my '87 Cougar and I am glad to see that your anaysis and selection criteria agrees with mine. Are you looking at the 4.57 ratio, I presume? 11.5% torque increase seems worhwhile and fuel mileage is not going to suffer much. I myself am going from a 2.73 ratio to a 3.55, which is a staggering 30% increase, and it'll still keep my freeway rpm just under 2k, which is great for a V8. Its fun to breathe a little new life into these older cars, isn't it? :)
Details mentioned that could be included: how to change the gear ratios, and what device/where do you get one to correct the speedometer. If they're mentioned (the first being kind of the tpoci), I'm thinking it's always good to include details. Great vid!
A big disadvantage you didn't mention is the effect to throttle response, say mid turn feathering the throttle. The 4.77 is very very jerky in these conditions and can often unsettle the rear end. Taller gearing smooths out the jerkiness at the expense of less torque. I think this is very important to mention.
Great video! Math checks out. Don't forget to mention gear whine. You go too short in the final drive and you will hear the rear end from inside the car.
Just wanted to say how much I enjoy your videos. I love cars and have always been fascinated with how they work. Your explanations of automotive systems make me appreciate the complexity and beauty of cars that much more. Thanks!
I changed the front and rear sprocket on my ZX10R because it would hit 105mph in first gear! I went down a tooth up front and up 3 teeth out back. Now it accelerates even better, but hits about 85 mph in first gear, making it a little more "practical".
I had an old mid 70's Chevelle that had 2.73 gearing. It was a complete pig off the line. (145 bhp/250 lb.-ft) With bigger 15 inch tires and enough road, I could do 155 mph/250 kph. I miss that old boat.
Amazing video as always! Esssentialy its like changing gears in a mountain bike. in 1st gear with the small disk every hard step at each pedal equals front tire lift off, and the more you switch to 2nd and 3rd disk in the pedals, less torque is generated from your own muscles instead of an engine :)
Great video Jason, I'm sure glad you haven't stopped saying your signature opening diaogue. it really sets you apart from the other guys. Again thank you.
Yes but you may be missing an important point, a car works better at a specific range of revs so by increasing that ratio can help you keep your can between those revs, like in heavy trucks
In computer gaming. I got a lot more performance out of cars by increasing the final drive ratio. Then, for the last manual gear I could use, I'd make it taller than how the car was stock. Why? Because I needed a higher top speed. It was extremely effective. Occasionally, when a track wouldn't work out if I did my normal adjustments, I'd go for a taller 2nd to last manual gear to meet in the middle. There was 1 track where even the last gear needed to be shorter and if it was like the scenario in this video, I even made the 6th gear shorter than the 5th gear. If you know exactly what you want a car purposed for, you can dial in gear ratios, if you don't, or if you just want a car that's more fun, but you don't want the highway to break the bank? Well..tough choices unless you can also change the "over drive" gear. Apologies, I was a bit vague on the final gear number, and I wasn't referring to the final gear ratio when I said last manual gear. I don't remember anymore how many gears I had to chose from.
Final drive ratios are not the most important thing. The most important thing is the actual ratio that reaches the wheels. If a truck with a 1st gear of 3.111 and a final drive of 4.848 has the exact same mechanical advantage as a truck with a first gear of 4.148 and a final drive of 3.636, when both are in first gear. That said, gearbox held constant, the final drive makes a huge difference!
But only at launch. With a taller final drive, you might find yourself in 3rd instead of 4th at a given speed, which would also boost torque. If you already have wheelspin in 1st then you have plenty of gear.
I just watched your car gears video from 2011, I must say, you have become a lot more confident and mature since then, and also glad you've ditched that 'High School Musical Zac Effron' hairdo
I have one complaint on this, about going to aggressive and loosing a gear because your top speed will switch to the next gear down depending on how aggressive you go. Yess your yop speed might just shift to the next gear down when going more aggressive, but... your low rpm, mph, will not be the same as your old gear once was. Top speed will be the sane as the old gear, but your bottom end mph will be different. Hard to explain in text. But day 5th took you from 30mph at 1500rpm to 100mph at 5000rpm Now with the more agressive gear, your 6th gear will be more around 40mph at the 1500rpm but still only taking you to 100mph at 5000rpm. It makes the gap smaller which is where you get the seat feel. The gap in mph to rpm is now tighter, giving you the feel of more power.
mitsubishi lancer , outlander sport and outlander final drive ratios are all above 6 ,stock.but because of cvt and a very low final gear ratio they cruise so very well on highway.
I learned alot of what you just went through by playing "GRAN turismo" when I was 12 years old. Guess I'm fortunate that way... I should of went to an engineering school because this stuff interests me to no end!!!!! Good Job ! AWESOME !!! Thank you for this contribution. MORE PLEASE ! lol
But at the same time, if your main acceleration metric is 0-60mph, a higher ratio final drive might induce an extra shift before 60mph, which depending on the shifting time, might end up being slower than the original FDR. Also, a higher wheel torque assumes you have the traction available to put down that torque. Alsooo, choosing an FDR ratio must take into consideration the fact that specific ratios may induce what's called "heterodyne effect", which destroys your cars NVH.
Agreed, though I don't think the 0-60 metric is the ideal metric to use for acceleration (after all, it's a unit of time, not acceleration). It doesn't tell you what you'll feel. Seconds 1-3 might be very different from seconds 4-6, for example.
well the power band of an engine dictates much of the qualities and characteristics of the acceleration. the powertrain system must be thought of as a unit, everything works together to get the result (work) done. how fast the work is done would be the unit of measure for 1/4 miles race. the amount of work ( load) can be measured in payload or hauling capacity. torque is most effective when hauling, hp is more effective when racing. but we must have both.
endoftheroad You won't notice the time on the street but that's more for dedicated drag races who that really matters to. 0-60 doesn't matter to manufacturers unless it's their flagship car
I cannot support this theory. my v8 suv with 3.73 gears os super slow off the line, but with 3.55 gears it is almost normal. however the toing capacity is much less.
Considering the average Joe will always say "my car does 0-60 in x seconds" and not "my car has a peak acceleration of 0.85g in first gear", 0-60mph times will always be a requirement for a powertrain configuration and one every manufacturer will consider when picking an FDR ratio
Fantastic video Jason very informative. I also own an 02 AP1 which I've been considering doing this for a while now as I had seen an original Japanese vtec club style video in which they put a very mildly tuned S2 against a standard AP1 and Ap2,the one which had the shorter final drive was very eager through the gears off the line. I know you was thinking of doing this modification on another previous video of yours I watched so keep us updated
What is the most efficient internal engine on the planet? Difference between cylinder size and their efficiencies? If I can say, you are the Neil Degrasse Tyson of the car world :) Thank you for your passion in your work! Very inspiring!
About the lower top speed thing. If you're driving in a vacuum then the top speed will be limited. But in the real world where there's air resistance. Changing the final drive won't necessarily reduce top speed. It's dependent on how much power the car's engine makes. For example a stock new edge Mustang GT with the manual has a theoretical top speed of about 219 MPH (24.9 inch tall tires, 3.27 axle ratio, and a 0.62 5th gear ratio). But obviously it won't have nearly enough power to reach that speed because the dread hand of aerodynamic drag will limit keep things to about 140 MPH. So if you were to change out the rear end gears to something like 3.73, the theoretical top speed will drop to around 191 MPH, but again because the engine doesn't produce enough power to reach that speed, the actual top speed will still be around 140 MPH. It might be a bit higher because the engine will be turning more RPM for any given speed and will be making more power when it hits top speed vs. having the stock rear end gearing.
one thing that could have been over looked in this video. if you do go to a lower final drive gear ratio, you will only get greater acceleration if you have enough traction. more torque is great but if you do not have good traction you are just spinning your wheels, literally.
various reasons, fuel efficiency, power efficiency, top speed......but you may also benefit from a down tuned gear ratio. Depending on the track or demand of power application
The real win for performance would be to map wheel torque vs. road speed, and find the final drive gearing that gives you the most space under the curve.
really nice video, i looked at others and this one made all of the other videos make sense. it kinda gave me the last puzzle piece if that makes sense.
Good information. What I miss from this video is information about acceleration in ranges that cross gears. Say 50-90 for instance. That would have you take one gear-change with the original ratio and two with the others. Another interesting range would be 0-100, where you would spend less time in the highest ratio with the original gearing.
This is a minimalist idea about modifying stock cars, you can have the same acceleration numbers results by increasing engine power, powerful engines require smaller differential and gearbox ratios. If you have big power and high gear ratios the result is lack of grip and spinning free wheels. Cheers
Application is everything when choosing a final drive ratio. How will the vehicle be used. Towing, race, everyday driver, or somewhere in between. The engines power curve is a big factor along with the transmission in deciding. If it doesn't work together as a unit it's not going to perform well at all. You can easily over gear and find you have run out of engine. I've seen plenty of guys do this.
Going for a shorter gear is good if you can bump your redline up some like 500rpm if you can make or hold power up that high. That way you don't have to shift earlier/you can hold the gear the same amount of time while keeping the benefit of multiplied torque down low and in the mid range.
In most cases, on petrol powered cars, a longer FD is needed. Here is what I mean : 3700 rpm at 70 mph is too much, especially if you have a loud af exhaust. I think manufacturers should take a page from their own book and do what they do on automatics, which is either add more gears, which on a manual is kind of hard, or give cars a longer 5th/6th gear.
I did a version of this on my RSX transmission, where I changed the final drive from a 4.3 to a 4.7, and I switched my 6 gear for a tsx 6th gear, also put an lsd in from an si.
Good explanation, also, if you're going to change the final drive, you can also upgrade to a better non crappy stock lsd (most stock lsd's are kind of pathetic in most cases, they may as well be called an open diff in all honesty) like a quaife in the process (not cheap, but considered the best for street use). Kind of a no brainer upgrade rather than throwing thousands at the engine unless you want to go forced induction and risk reliability. This is my next mod after the lighter weight 2 piece rotors/pads/fluid and exhaust is changed. Now if we only had shops in Oregon that had people that actually know how to properly install parts (staff that's worked there for greater than 6 months..), now THAT should be your next video! Best shops in the NW and why (besides Cobb in Tigard because not everyone wants a ME TOO subaru right?).
Random question, since you are amazing at explaining mathematical calculations could you do a video explaining what is more efficient when heating a house in the winter, if keeping your furnace set to one constant temperature is more efficient than lowering it during the day and raising it back up at night. I'm sure the formula involves rate of heat dissipation and the rate in which the furnace can pump out heat Vs the energy it uses doing so, now I wonder if the heat dissipating is a constant variable or if house is warmer it dissipates faster, thanks if you get around to looking into this, great channel btw always watch your videos
I would check that second gear on the 4.10 again. I autocross my stock 2003 AP1 and my 2nd gear bounces at 63ish.... no where close to 68mph. And the info on S2ki confirms.
I was looking for 3.90 or better in a truck for towing. Got one with a tow package @ 4.30. I would have been happy with 4.10, but Im not going to be picky since I didn't have to get my hands dirty. It kills MPG but sure is handy backing up a trailer or off-road.
Correction: The speedo will NOT become incorrect by changing final drive ratio. Speed is usually calculated by measuring revolutions at the wheels (via an odometer that is also used for ABS and ESP) and taking the known wheel circumference into account. This is not at all influenced by gearing. The only way that gearing could have an effect on the speedometer reading was if the speed was calculated from RPM multiplied by the gearing currently in effect.
Not necessarily - some cars use a sensor to measure rotations of the differential gear for speed (usually called a vehicle speed sensor as opposed to a wheel speed sensor) - in this case changing final drive (i.e. number of teeth on the ring gear) does effect the speedo unless a new speed sensor gear is installed to compensate
very informative! great video! I'm catching up to you buddy.... been working at a mechanic shop! really liked your detailed explanation about why and how the final drive crossover basically can be the meaningless to have it be more aggressive. @4:15 if your're looking at a graph. very informative. keep killing it. love your videos
this is why high end sport saloons have 8 speed auto gearboxes. if you put a porsche panamera into sport mode it will reach its top speed in 6th gear. the 7th and 8th gears are just for saving fuel while blasting on the autobahn.
I switched out 3.73 to 4.56 in my diesel truck after moving to 37" tires. It accelerates a lot quicker but I don't care for the high interstate rpm. I should have gone with 4.10.
I have recently gotten into your videos and they are very well done. I like learning about vehicles the way you teach. I would just like to ask if you can make, if you have not already made, a video on why all four tires need to be changed at the same time on a 4x4 when you get a popped tire/low tread. Thank you!
Very nicely explained for a person like me who does not have any engineering background. So can we vary the FD ratio on the fly ?? like switching between the "Eco mode" to "sports mode" ???
axle ratio play an important role in commercial vehicle as well. Both fuel consumption and weight carrying capacity are vital. Assuming a vehicle carrying a fix amount of weight and cruising at a constant speed, reducing the axle ratio will contribute in fuel saving however it will greatly impact the wheel torque due to decrease in engine rpm (from engine torque curve). At what axle ratio the vehicle will not produce enough wheel torque allowing the vehicle to travel at the same speed and load? thx
You need better rear axle/subframe bushings and reinforcement to compensate the increased torque transmitted by the differential. And engine wears faster due to higher rev.
can you also explain how acceleration will be affected and by how much? i. e. 0-60 mph and 40-70 in this particular case? I think that's main reason why people changing final drives...
Does wheel size, example going from a 15" to a 16" wheel or other way around, affect your top speed or wheel torque in any way? and if so how exactly? great video btw, love these kinds of videos.
+Dark Winter if your tire diameter remains the exact same (can be difficult to match perfectly), then no. If your tire diameter does change, then so will your gearing/speed/etc.
The real question is: why should I have to make any trade offs? When 4-speeds appeared, everyone got exceeded because they thought they were getting an awesome low first gear and could still have low RPM on the highway. Instead they got the same ratio between 1st and 4th as they had between 1st and 3rd on their old car. No matter what final drive you tried, you lost something. * sad trombone * Then all the cars got 5 speeds. Does this mean we now get a real choice of gears, for any situation? Nope. Same ratio between 1st and 5th as you had between 1st and 4th. If anything, the ratios were getting closer. Now people are staring to get annoyed. Marketing has the solution: "close ratio transmission®". What the hell is that? It's what all the race cars have. You'll love it. If it's good for racing, it's good for you. Really. We'll paint some stripes on the car to go with it. Uh...? Then came SIX speeds! And.... * sad trombone * They keep giving you more gears to play with, but less and less that you can actually do with them.
Great vid! You should totally make a vid on the benefits of the FRIC suspension systems that F1 teams use. I think that stuff is super interesting! Thanks!
whatever you do with your diff ,you have to know something - it's much better when cruising at 2000 rpm rather than 4000 rpm. Plus when cruising at lower RPM every other component in the engine bay will wear much less . So logner diff is the one to get. Shorter diff sucks on highway and on any place except track . Nomather if your car is quicker or not , if you need more power hust swap the engine with bigger.
Arthur Friday yeah, cause I know with 4WD you have to have the same gears otherwise your drivetrain will lock up, I just have trouble understanding how the system integrates between the rear and the front, and why they need to be the same, or different with different sized wheels.
Not such a huge deal with AWD because of the center differential (allows the front and rear to turn at different speeds). The reason you need equivalent ratios with 4WD is because it doesn't allow the front and rear to turn at different speeds. Can you see why that might be a rather large problem?
On 4wd the transmission inputs power to the transfer case. When the case is in 4 hi or 4 low it mechanically locks the front and rear outputs to the same speed. If the front wheels were smaller, in 4wd they wouldn't spin fast enough if the axles had the same ratio.
Great stuff. Is there a chart online that we can go to that shows what happens to the top speed if we change the gear? For example, if I have a 2011 wrx and I want to change the gear, is there a chart on line I can go to to see my options and what will be the differences?
A shorter final drive ratio will not necessarily lead to higher wheel torque when you put speed as a constant. E.g. With a stock final drive, a b series honda will hit 100kph at second gear @ 8000 rpm. With a short final drive, at 100kph, the car needs to be put in 3rd gear at 6000 rpm, which produces less wheel torque. The car with the stock final drive will accelerate to 101kph faster than the other. Yes, engine torque is higher at 6k rpm but wheel torque is lower. Top wheel torque rpm matches top hp rpm, with any given gear. You cannot conclude that a shorter final drive ratio would mean better acceleration. One cannot look at final drive ratio separately from its gear ratios. It's a harmony between the 2. Plot a graph of speed against torque using all the gears for each final drive, then you will see which final drive suits the track best (kept at high rpms)
the difference between car enthusiast and an engineer, they know how car works but dont understand what makes a car fun. i remember he picked turbo over supercharger because of how the efficiency it is compare to s/c. then after he drove a s/c he understood the power delivery was linear that of stock engine but more power. thats when he understood what makes a car enjoyable its the same thing why i thought pruis was cool when it first came out. not because how it dive but how it was in conjunction to engine and electric motor.
Thank you for providing info on this topic. After reviewing the technical specs of my 2015 VW Golf R, I'm left scratching my head... the tech specs list the following, Final I 4.77 and Final Ii
Just a way VW handles their transmissions. They have a different final drive for gears 5 & 6 on many of their manual transmissions, perhaps others too.
The computer in my car limits my top speed to 162 mph. With going to a higher gear allows me to still have the 162 mph top speed but it helps my cars acceleration and makes it easier on my clutch also getting my car’s perfect rpm range faster.
What's your opinion on the Kia/Hyundai DCT-7 coupled to the 4 cyl. 1.6 I Turbo GDI? These are the gear ratios 7-Speed Dual-Clutch Transmission (DCT) - - First - 3.786:1 Second - 2.261:1 Third - 1.957:1 Fourth - 1.023:1 Fifth - 0.778:1 Sixth - 0.837:1 Seventh - 0.681:1 Reverse - 5.074:1 Final gear ratio - 4.786:1 (1/2/4/5) / 3.526:1 (3/6/7/R) Clutch type - Dry type double plate
Thank you for the explanations (and the other video with the tests on the Honda), luckily for me all the downsides are meaningless since I am going to modify a track car
Changing the F.D in an auto significantly to the point of eliminating a gear, I imagine would be more advantageous than in a manual. For the simple fact you would loose 6th but obtain a gear lower than 1st. I imagine an auto would make better use of this "new" gear as it would be only useful for such a small speed range, ie launching from a start
Engineering explained... I prochargered my 14 v6 mustang and stuck w the 2.73 stock gear ratio. So far so good, would you recommend switching out? I know 3.73 would be too much, but I'm afraid 3.31 would not be much noticeable.
figuring out your cars drag limited top speed based on its drag ratio, gearing and hp could be a interesting video. might be too complicated math wise for a video though. idk
"And you're gonna hit vtec at some point"
That is gold.
I don't get it
@bernie3075 you have to understand vtec first
I love how casually he mentions VTEC
I want the 1989 gtr vtec
S2000
@Randy Candelario no vtec is not lame, but people like you are
Why are they lame?
@alexandremelo7656 what is vtec
Also changing final drive to a more aggressive set up can also increase the amount of times you need to shift in order to reach 60mph and may alter acceleration time.
I believe the proper term is "VTEC Yo!"
wow, that old gears video... your marker skills have improved greatly on the whiteboard.
Great info, why don't manufacturers put super tall 6th gears in? If I'm on interstate and have to downshift no big deal, that's what I signed up for by driving manual.
+mike anderson I don't know, I wish they did. Mustangs are the only cars I know of that do this really well. Love Mustang gearing.
Engineering Explained how about other gears. why do manufacturers sometimes seem to spec ratios outside the peak efficiency range?
The Viper had a very tall 6th gear, 0.50 :1 for 6th, the 4th gen F-Bodies had the same T-56 and also had tall 6th gears.
My '95 Z28 M6 has a plenty steep 6th gear, cruising at almost idle doing 70. Obviously a Honda won't be doing that because it has no torque, maybe a better question is, why do they make so many cars that are completely gutless at lower rpm's?
Jeff Smith they do, but those cars dont have top end
years ago when i was street racing with a 79 monty with a 355 and 3 speed auto I learned a lot of this the hard way. my car was traction limited by the real wheel size i could fit and my transmission ratios were set in stone because I couldn't afford to change the ratios or add a OD. I did run a much looser converter 3500 rpm. after doing some testing and basic math I figured out a 4.56:1 ratio would be the best ratio for 1/4 mile, because it would let me run through the traps in 3rd near my TQ peak, I also learned the 4.56: would over power the traction limits of my rear tires with the suspension setup i had at the time. it took a bit of tweaking with the geometry of the 4 bars to get the pinion angle corrected and the reaction of the setup to plant the tires instead of wheel hopping and wasting energy twisting things. this was around 30 years ago. thanks for the videos that shed some new light on things
Militaristics Wow! 4.56 for 1/4 drag race!? How tall were your tires? 32+s? In the 90's I used to bracket race my old 1977 Trans Am with 4 speed in the 1/8 mile. It had a 3.73 final and 28 inch tall tires (275/60r15). It had a warmed over 400 Pontaic with Edelbrock heads. Cruising 70 mph down the highway the engine was running just over 3k. Didn't even need to down shift to pass. I can't imagine what 4.56 gears would do in that thing.
i remember running 26 or 28 in tall tires on that car with a powerband of 4500-7500 so that's why i ran the 4.56's crusing rpm wasn't a big factor as I did not drive the car for any distance and couldn't afford a gear vendors OD unit.
Thank you so much for thinking of all non-Americans :) Love your channel, keep up the great work! Best wishes from Germany
I've tried to explain this subject to some of my knucklehead friends who think that the taller (numerically) the gear, the faster you'll go in a quarter mile. Yes, to a certain extent, but the elapsed times, and more so, MPH, will eventually drop off. I know this because I experienced it in my own racing career. This video explains very well what happens, so I'll be sending this link to some friends. But, alas, they probably still won't get it.
Thank you for the great explanation! I am doing a rear end swap on my '87 Cougar and I am glad to see that your anaysis and selection criteria agrees with mine. Are you looking at the 4.57 ratio, I presume? 11.5% torque increase seems worhwhile and fuel mileage is not going to suffer much. I myself am going from a 2.73 ratio to a 3.55, which is a staggering 30% increase, and it'll still keep my freeway rpm just under 2k, which is great for a V8. Its fun to breathe a little new life into these older cars, isn't it? :)
Consider strengthening your driveline, especially for the drag strip. I snapped an axle at the line, and that was on foot wide drag radials.
Details mentioned that could be included: how to change the gear ratios, and what device/where do you get one to correct the speedometer. If they're mentioned (the first being kind of the tpoci), I'm thinking it's always good to include details. Great vid!
I would tune the car the other way, increasing the top speed to finally get a lower rpm when driving on the highway (especially with older cars...)
A big disadvantage you didn't mention is the effect to throttle response, say mid turn feathering the throttle. The 4.77 is very very jerky in these conditions and can often unsettle the rear end. Taller gearing smooths out the jerkiness at the expense of less torque. I think this is very important to mention.
Like a 2.41 or 2.28 gear in the old GM cars? Or is there a cut off where u loose ALL performance potential?
Can you do a similar video in relation to increase/decrease in wheel and tire sizes?
Going from 3.21 to 3.92 in my truck tomorrow. Also dropping a positraction in. With 8 Gears I'm not too worried about top speed suffering.
Great video! Math checks out. Don't forget to mention gear whine. You go too short in the final drive and you will hear the rear end from inside the car.
Just wanted to say how much I enjoy your videos. I love cars and have always been fascinated with how they work. Your explanations of automotive systems make me appreciate the complexity and beauty of cars that much more. Thanks!
There's also added stress on components. Axles come to mind.
Johnny Doe I was thinking the same thing... If you Increase torque you'd better increase axles.. and supporting components. ..👀👍™
not really, your tyres will break traction before your axles start deforming
not if you have good tires. Axles and drive shafts break alot. ...
Karlos understands it and depending on the car's age and condition it should be able to handle it unless you go over the top
No need to worry about a stock S2000 breaking any axels though. They are only rated at 162lb-ft of torque. lol
Thanks for the Km/h chart!
Did u change the FDR of ur S2000, if ur planning, pls dont forgot to film it.. Nice video as always.. Thanks
Nice video, as always. One thing though, the 4.77 gears are a LOWER gear than the 4.1. You stated it the other way around (at 4:48 & 4:55 time).
I changed the front and rear sprocket on my ZX10R because it would hit 105mph in first gear! I went down a tooth up front and up 3 teeth out back. Now it accelerates even better, but hits about 85 mph in first gear, making it a little more "practical".
Thanks this helped a lot I play way too much pixel car racer and didn't understand final drive but now I have perfect torque.
I had an old mid 70's Chevelle that had 2.73 gearing. It was a complete pig off the line. (145 bhp/250 lb.-ft) With bigger 15 inch tires and enough road, I could do 155 mph/250 kph. I miss that old boat.
I learned much of this while tuning cars trial and error style in Forza racing games, but I didn't know that until I watched this...
Amazing video as always! Esssentialy its like changing gears in a mountain bike. in 1st gear with the small disk every hard step at each pedal equals front tire lift off, and the more you switch to 2nd and 3rd disk in the pedals, less torque is generated from your own muscles instead of an engine :)
i learn more in this video than a semester in physics class
Great video Jason, I'm sure glad you haven't stopped saying your signature opening diaogue. it really sets you apart from the other guys. Again thank you.
Yes but you may be missing an important point, a car works better at a specific range of revs so by increasing that ratio can help you keep your can between those revs, like in heavy trucks
I did not know gear ratios affect speedometer readings, thanks for that info bruv.
Thanks! Now I can fine tune my drag car in pixel car racer
Ancel Curativo Bout to make that sub 6 drag car
In computer gaming. I got a lot more performance out of cars by increasing the final drive ratio. Then, for the last manual gear I could use, I'd make it taller than how the car was stock. Why? Because I needed a higher top speed. It was extremely effective.
Occasionally, when a track wouldn't work out if I did my normal adjustments, I'd go for a taller 2nd to last manual gear to meet in the middle.
There was 1 track where even the last gear needed to be shorter and if it was like the scenario in this video, I even made the 6th gear shorter than the 5th gear.
If you know exactly what you want a car purposed for, you can dial in gear ratios, if you don't, or if you just want a car that's more fun, but you don't want the highway to break the bank? Well..tough choices unless you can also change the "over drive" gear.
Apologies, I was a bit vague on the final gear number, and I wasn't referring to the final gear ratio when I said last manual gear. I don't remember anymore how many gears I had to chose from.
Final drive ratios are not the most important thing. The most important thing is the actual ratio that reaches the wheels. If a truck with a 1st gear of 3.111 and a final drive of 4.848 has the exact same mechanical advantage as a truck with a first gear of 4.148 and a final drive of 3.636, when both are in first gear.
That said, gearbox held constant, the final drive makes a huge difference!
ExactlyPrecisely well no duh. He's comparing swapping the fd on the same car. He didn't mention anything about comparing car to car...
But only at launch. With a taller final drive, you might find yourself in 3rd instead of 4th at a given speed, which would also boost torque. If you already have wheelspin in 1st then you have plenty of gear.
I just watched your car gears video from 2011, I must say, you have become a lot more confident and mature since then, and also glad you've ditched that 'High School Musical Zac Effron' hairdo
I have one complaint on this, about going to aggressive and loosing a gear because your top speed will switch to the next gear down depending on how aggressive you go. Yess your yop speed might just shift to the next gear down when going more aggressive, but... your low rpm, mph, will not be the same as your old gear once was. Top speed will be the sane as the old gear, but your bottom end mph will be different. Hard to explain in text. But day 5th took you from 30mph at 1500rpm to 100mph at 5000rpm
Now with the more agressive gear, your 6th gear will be more around 40mph at the 1500rpm but still only taking you to 100mph at 5000rpm. It makes the gap smaller which is where you get the seat feel. The gap in mph to rpm is now tighter, giving you the feel of more power.
mitsubishi lancer , outlander sport and outlander final drive ratios are all above 6 ,stock.but because of cvt and a very low final gear ratio they cruise so very well on highway.
I learned alot of what you just went through by playing "GRAN turismo" when I was 12 years old. Guess I'm fortunate that way... I should of went to an engineering school because this stuff interests me to no end!!!!! Good Job ! AWESOME !!! Thank you for this contribution. MORE PLEASE ! lol
I've got a close ratio box in my Suzuki and it's fantastic, though I wish 5th were a bit longer - doing 4k rpm while cruising is a bit irritating
Thanks now I can tune my car on forza horizon 3 hhaha
TheOnlyHMR I used em for grand Trismo lol
go with 4.77 final drive ratio. you can take off like a rocket.
But at the same time, if your main acceleration metric is 0-60mph, a higher ratio final drive might induce an extra shift before 60mph, which depending on the shifting time, might end up being slower than the original FDR. Also, a higher wheel torque assumes you have the traction available to put down that torque. Alsooo, choosing an FDR ratio must take into consideration the fact that specific ratios may induce what's called "heterodyne effect", which destroys your cars NVH.
Agreed, though I don't think the 0-60 metric is the ideal metric to use for acceleration (after all, it's a unit of time, not acceleration). It doesn't tell you what you'll feel. Seconds 1-3 might be very different from seconds 4-6, for example.
well the power band of an engine dictates much of the qualities and characteristics of the acceleration. the powertrain system must be thought of as a unit, everything works together to get the result (work) done. how fast the work is done would be the unit of measure for 1/4 miles race. the amount of work ( load) can be measured in payload or hauling capacity. torque is most effective when hauling, hp is more effective when racing. but we must have both.
endoftheroad
You won't notice the time on the street but that's more for dedicated drag races who that really matters to. 0-60 doesn't matter to manufacturers unless it's their flagship car
I cannot support this theory. my v8 suv with 3.73 gears os super slow off the line, but with 3.55 gears it is almost normal. however the toing capacity is much less.
Considering the average Joe will always say "my car does 0-60 in x seconds" and not "my car has a peak acceleration of 0.85g in first gear", 0-60mph times will always be a requirement for a powertrain configuration and one every manufacturer will consider when picking an FDR ratio
Fantastic video Jason very informative. I also own an 02 AP1 which I've been considering doing this for a while now as I had seen an original Japanese vtec club style video in which they put a very mildly tuned S2 against a standard AP1 and Ap2,the one which had the shorter final drive was very eager through the gears off the line. I know you was thinking of doing this modification on another previous video of yours I watched so keep us updated
great info. next question: how do manufacturers decide the gear ratio, why does it sometimes ignore peak torque?
This may help you out! th-cam.com/video/zZBqb0ZJSwU/w-d-xo.html
Thanks for releasing this on the same day I (likely, pending tear down,) blew up my final drive.
What is the most efficient internal engine on the planet? Difference between cylinder size and their efficiencies? If I can say, you are the Neil Degrasse Tyson of the car world :) Thank you for your passion in your work! Very inspiring!
About the lower top speed thing. If you're driving in a vacuum then the top speed will be limited. But in the real world where there's air resistance. Changing the final drive won't necessarily reduce top speed. It's dependent on how much power the car's engine makes. For example a stock new edge Mustang GT with the manual has a theoretical top speed of about 219 MPH (24.9 inch tall tires, 3.27 axle ratio, and a 0.62 5th gear ratio). But obviously it won't have nearly enough power to reach that speed because the dread hand of aerodynamic drag will limit keep things to about 140 MPH. So if you were to change out the rear end gears to something like 3.73, the theoretical top speed will drop to around 191 MPH, but again because the engine doesn't produce enough power to reach that speed, the actual top speed will still be around 140 MPH. It might be a bit higher because the engine will be turning more RPM for any given speed and will be making more power when it hits top speed vs. having the stock rear end gearing.
one thing that could have been over looked in this video. if you do go to a lower final drive gear ratio, you will only get greater acceleration if you have enough traction. more torque is great but if you do not have good traction you are just spinning your wheels, literally.
that could be an intended effect
various reasons, fuel efficiency, power efficiency, top speed......but you may also benefit from a down tuned gear ratio. Depending on the track or demand of power application
The real win for performance would be to map wheel torque vs. road speed, and find the final drive gearing that gives you the most space under the curve.
really nice video, i looked at others and this one made all of the other videos make sense. it kinda gave me the last puzzle piece if that makes sense.
Good information. What I miss from this video is information about acceleration in ranges that cross gears. Say 50-90 for instance. That would have you take one gear-change with the original ratio and two with the others. Another interesting range would be 0-100, where you would spend less time in the highest ratio with the original gearing.
This is a minimalist idea about modifying stock cars, you can have the same acceleration numbers results by increasing engine power, powerful engines require smaller differential and gearbox ratios. If you have big power and high gear ratios the result is lack of grip and spinning free wheels. Cheers
Application is everything when choosing a final drive ratio. How will the vehicle be used. Towing, race, everyday driver, or somewhere in between. The engines power curve is a big factor along with the transmission in deciding. If it doesn't work together as a unit it's not going to perform well at all. You can easily over gear and find you have run out of engine. I've seen plenty of guys do this.
I'm just be in here. Sorry for asking, what i'm understand here is, if the final ratio is lower, then the top speed will increase? It's that true?
Best way to understand that is playing with custom gear ratios in Grand Turismo (car video game on Playstation).
Going for a shorter gear is good if you can bump your redline up some like 500rpm if you can make or hold power up that high. That way you don't have to shift earlier/you can hold the gear the same amount of time while keeping the benefit of multiplied torque down low and in the mid range.
A short video on over/under drives would be a nice follow up to this.
I believe the definition essentially comes down to having a gear ratio under 1 for overdrive.
As always, very well explained and simple understanding!
We appreciate ya'
Thank you sir
thanks! now i understand what is final drive ratio
U got really good skill in delivering information
In most cases, on petrol powered cars, a longer FD is needed. Here is what I mean : 3700 rpm at 70 mph is too much, especially if you have a loud af exhaust. I think manufacturers should take a page from their own book and do what they do on automatics, which is either add more gears, which on a manual is kind of hard, or give cars a longer 5th/6th gear.
Eliminating a gear (or adding a granny gear) can be desirable for trucks that tow or off-road vehicles where 1st gear torque matters.
you buy a Scania with 730hp and no problem
Nice explanation that clear and easy to understanding!
I did a version of this on my RSX transmission, where I changed the final drive from a 4.3 to a 4.7, and I switched my 6 gear for a tsx 6th gear, also put an lsd in from an si.
Did the 4.7 make any noticeable changes in acceleration?
SD70ace_railfan it’s not a big difference, it feels more rev happy though. The 4.3 is better if you plan to do turbo though.
Good explanation, also, if you're going to change the final drive, you can also upgrade to a better non crappy stock lsd (most stock lsd's are kind of pathetic in most cases, they may as well be called an open diff in all honesty) like a quaife in the process (not cheap, but considered the best for street use). Kind of a no brainer upgrade rather than throwing thousands at the engine unless you want to go forced induction and risk reliability. This is my next mod after the lighter weight 2 piece rotors/pads/fluid and exhaust is changed. Now if we only had shops in Oregon that had people that actually know how to properly install parts (staff that's worked there for greater than 6 months..), now THAT should be your next video! Best shops in the NW and why (besides Cobb in Tigard because not everyone wants a ME TOO subaru right?).
Random question, since you are amazing at explaining mathematical calculations could you do a video explaining what is more efficient when heating a house in the winter, if keeping your furnace set to one constant temperature is more efficient than lowering it during the day and raising it back up at night. I'm sure the formula involves rate of heat dissipation and the rate in which the furnace can pump out heat Vs the energy it uses doing so, now I wonder if the heat dissipating is a constant variable or if house is warmer it dissipates faster, thanks if you get around to looking into this, great channel btw always watch your videos
I would check that second gear on the 4.10 again. I autocross my stock 2003 AP1 and my 2nd gear bounces at 63ish.... no where close to 68mph. And the info on S2ki confirms.
I was looking for 3.90 or better in a truck for towing. Got one with a tow package @ 4.30. I would have been happy with 4.10, but Im not going to be picky since I didn't have to get my hands dirty. It kills MPG but sure is handy backing up a trailer or off-road.
Perfectly explained. Exactly the information I was looking for. Thank you very much.
Correction: The speedo will NOT become incorrect by changing final drive ratio. Speed is usually calculated by measuring revolutions at the wheels (via an odometer that is also used for ABS and ESP) and taking the known wheel circumference into account. This is not at all influenced by gearing. The only way that gearing could have an effect on the speedometer reading was if the speed was calculated from RPM multiplied by the gearing currently in effect.
Not necessarily - some cars use a sensor to measure rotations of the differential gear for speed (usually called a vehicle speed sensor as opposed to a wheel speed sensor) - in this case changing final drive (i.e. number of teeth on the ring gear) does effect the speedo unless a new speed sensor gear is installed to compensate
very informative! great video! I'm catching up to you buddy.... been working at a mechanic shop! really liked your detailed explanation about why and how the final drive crossover basically can be the meaningless to have it be more aggressive. @4:15 if your're looking at a graph. very informative. keep killing it. love your videos
Commonly done with offroad vehciles when you up tire/wheel size. Need to regain some of that lost power so you regear to compensate.
this is why high end sport saloons have 8 speed auto gearboxes. if you put a porsche panamera into sport mode it will reach its top speed in 6th gear. the 7th and 8th gears are just for saving fuel while blasting on the autobahn.
I switched out 3.73 to 4.56 in my diesel truck after moving to 37" tires. It accelerates a lot quicker but I don't care for the high interstate rpm. I should have gone with 4.10.
I have recently gotten into your videos and they are very well done. I like learning about vehicles the way you teach. I would just like to ask if you can make, if you have not already made, a video on why all four tires need to be changed at the same time on a 4x4 when you get a popped tire/low tread. Thank you!
Very nicely explained for a person like me who does not have any engineering background. So can we vary the FD ratio on the fly ?? like switching between the "Eco mode" to "sports mode" ???
axle ratio play an important role in commercial vehicle as well. Both fuel consumption and weight carrying capacity are vital. Assuming a vehicle carrying a fix amount of weight and cruising at a constant speed, reducing the axle ratio will contribute in fuel saving however it will greatly impact the wheel torque due to decrease in engine rpm (from engine torque curve). At what axle ratio the vehicle will not produce enough wheel torque allowing the vehicle to travel at the same speed and load? thx
You need better rear axle/subframe bushings and reinforcement to compensate the increased torque transmitted by the differential. And engine wears faster due to higher rev.
can you also explain how acceleration will be affected and by how much? i. e. 0-60 mph and 40-70 in this particular case? I think that's main reason why people changing final drives...
I just bought 4.77 fd for my s2000 and I find this video! Subbed!
Love your videos, please could you explain why subaru ppp recommends larger wheels with their remap to take advantage of the gained torque
Does wheel size, example going from a 15" to a 16" wheel or other way around, affect your top speed or wheel torque in any way? and if so how exactly? great video btw, love these kinds of videos.
+Dark Winter if your tire diameter remains the exact same (can be difficult to match perfectly), then no. If your tire diameter does change, then so will your gearing/speed/etc.
The real question is: why should I have to make any trade offs?
When 4-speeds appeared, everyone got exceeded because they thought they were getting an awesome low first gear and could still have low RPM on the highway. Instead they got the same ratio between 1st and 4th as they had between 1st and 3rd on their old car. No matter what final drive you tried, you lost something.
* sad trombone *
Then all the cars got 5 speeds. Does this mean we now get a real choice of gears, for any situation? Nope. Same ratio between 1st and 5th as you had between 1st and 4th. If anything, the ratios were getting closer.
Now people are staring to get annoyed. Marketing has the solution: "close ratio transmission®". What the hell is that? It's what all the race cars have. You'll love it. If it's good for racing, it's good for you. Really. We'll paint some stripes on the car to go with it. Uh...?
Then came SIX speeds! And.... * sad trombone *
They keep giving you more gears to play with, but less and less that you can actually do with them.
Great vid! You should totally make a vid on the benefits of the FRIC suspension systems that F1 teams use. I think that stuff is super interesting! Thanks!
whatever you do with your diff ,you have to know something - it's much better when cruising at 2000 rpm rather than 4000 rpm. Plus when cruising at lower RPM every other component in the engine bay will wear much less . So logner diff is the one to get. Shorter diff sucks on highway and on any place except track . Nomather if your car is quicker or not , if you need more power hust swap the engine with bigger.
Hey, Jason, could you possibly explain how final drive ratios work in vehicles with transfer cases and/or AWD?
Arthur Friday yeah, cause I know with 4WD you have to have the same gears otherwise your drivetrain will lock up, I just have trouble understanding how the system integrates between the rear and the front, and why they need to be the same, or different with different sized wheels.
Not such a huge deal with AWD because of the center differential (allows the front and rear to turn at different speeds). The reason you need equivalent ratios with 4WD is because it doesn't allow the front and rear to turn at different speeds. Can you see why that might be a rather large problem?
On 4wd the transmission inputs power to the transfer case. When the case is in 4 hi or 4 low it mechanically locks the front and rear outputs to the same speed. If the front wheels were smaller, in 4wd they wouldn't spin fast enough if the axles had the same ratio.
Great job at explaining everything.
if you have a high reving engine like your honda, theres no reason to make gears shorter, thats why its better to go longer than shorter when boosted.
Great stuff. Is there a chart online that we can go to that shows what happens to the top speed if we change the gear?
For example, if I have a 2011 wrx and I want to change the gear, is there a chart on line I can go to to see my options and what will be the differences?
A shorter final drive ratio will not necessarily lead to higher wheel torque when you put speed as a constant.
E.g. With a stock final drive, a b series honda will hit 100kph at second gear @ 8000 rpm. With a short final drive, at 100kph, the car needs to be put in 3rd gear at 6000 rpm, which produces less wheel torque. The car with the stock final drive will accelerate to 101kph faster than the other. Yes, engine torque is higher at 6k rpm but wheel torque is lower. Top wheel torque rpm matches top hp rpm, with any given gear.
You cannot conclude that a shorter final drive ratio would mean better acceleration.
One cannot look at final drive ratio separately from its gear ratios. It's a harmony between the 2. Plot a graph of speed against torque using all the gears for each final drive, then you will see which final drive suits the track best (kept at high rpms)
the difference between car enthusiast and an engineer, they know how car works but dont understand what makes a car fun. i remember he picked turbo over supercharger because of how the efficiency it is compare to s/c. then after he drove a s/c he understood the power delivery was linear that of stock engine but more power. thats when he understood what makes a car enjoyable
its the same thing why i thought pruis was cool when it first came out. not because how it dive but how it was in conjunction to engine and electric motor.
Clear and detailed explanation. Thank you!
Thank you for providing info on this topic. After reviewing the technical specs of my 2015 VW Golf R, I'm left scratching my head... the tech specs list the following, Final I 4.77 and Final Ii
Final II 3.44
Sorry for the multiple posts; any idea why I have two final drives?
Just a way VW handles their transmissions. They have a different final drive for gears 5 & 6 on many of their manual transmissions, perhaps others too.
Rearwheel drive, VTEC... Is this car yellow by any chance?
The computer in my car limits my top speed to 162 mph. With going to a higher gear allows me to still have the 162 mph top speed but it helps my cars acceleration and makes it easier on my clutch also getting my car’s perfect rpm range faster.
What's your opinion on the Kia/Hyundai DCT-7 coupled to the 4 cyl. 1.6 I Turbo GDI? These are the gear ratios
7-Speed Dual-Clutch Transmission (DCT) - -
First - 3.786:1
Second - 2.261:1
Third - 1.957:1
Fourth - 1.023:1
Fifth - 0.778:1
Sixth - 0.837:1
Seventh - 0.681:1
Reverse - 5.074:1
Final gear ratio - 4.786:1 (1/2/4/5) / 3.526:1 (3/6/7/R)
Clutch type - Dry type double plate
Thank you for the explanations (and the other video with the tests on the Honda), luckily for me all the downsides are meaningless since I am going to modify a track car
Changing the F.D in an auto significantly to the point of eliminating a gear, I imagine would be more advantageous than in a manual. For the simple fact you would loose 6th but obtain a gear lower than 1st. I imagine an auto would make better use of this "new" gear as it would be only useful for such a small speed range, ie launching from a start
Engineering explained... I prochargered my 14 v6 mustang and stuck w the 2.73 stock gear ratio. So far so good, would you recommend switching out? I know 3.73 would be too much, but I'm afraid 3.31 would not be much noticeable.
Still have the car?
figuring out your cars drag limited top speed based on its drag ratio, gearing and hp could be a interesting video. might be too complicated math wise for a video though. idk