I am an automotive machinist. Been in the trade since 1990. I had a thrust bearing issue in my 94 C1500 4.3 V6 4L60E transmission. Owned the truck since new. It developed an odd rattle only under acceleration right outside of the warranty. Oil pressure was never an issue. Ran fine just that annoying rattle. About 95K the engine developed a dead miss. One cylinder had low compression. Made all the checks and discovered that a lifter was pumped up. Went in after the lifter issue. Drained the coolant. Got a little coolant in the oil so drained that out. I decided to pull the inspection cover off of the transmission and it was then I realized the thrust bearing was gone. Those V6 engines had an external balance weight on the flex plate and that was the noise I was hearing. The counter weight was hitting the back of the block. It did that for over 40k miles. Like yourself I had to try and figure out what the culprit was. I towed a smaller jet boat. Nothing giant. Couldn’t tell you the weight. The truck never even acted like it was hauling a load. Still yet all the mechanics I did machine work for told me that hauling anything with truck should not be done in overdrive. I did not know that. Then came the ballooned converter story. I had it checked out. Nothing was wrong with the converter or transmission. Took it to the shop I worked at and had the crank thrust welded and ground the crankshaft. All was like brand new. I never figured out anything direct. Could have been the towing I’ve just seen others tow heavier in the same type truck and never have any issues. Chalked it up to some times things happen and you don’t know why. That rebuild lasted for another 200K with no thrust issues. My daughter drove it to school for a year or two. All the single mothers my wife worked with drove it while they were saving for car repairs. Quite honestly I didn’t see the truck its last several years on the road. My niece was the last to drive it and called my wife to come get it. It was tired and worn out and I bet the oil change intervals were sad. One interesting issue surrounding thrust bearings arose while I was working for a machine shop that built very high end racing engines. Most for NHRA super comp dragsters. Several national title holders we built engines for. The shop had a great reputation for quality work. On one particular engine the thrust bearing issue paid a visit. Chewed up a $2500 crank shaft just the same way you’re looking at. You don’t weld these cranks up and turn them. You buy another brand new crankshaft. This was happening rapidly. Normally performance engines have a two part warranty. Breaks in two pieces you keep both pieces. In this case we had to do the work and buy the parts. It happened again. We asked the car owner to check this and that. “Ballooned converter”. Nothing doing. Then the third time around another racer that was our customer was gracious enough to help out the engine back in the car and that’s when the issue was noticed. It was a dragster with a four link rear end and a very short drive shaft. The four link was not adjusted correctly forcing the driveshaft too far into the transmission Bellhousing. The car owner was obviously sick. The very expensive two speed power glide had to be sent in for checks. The car was out back together and that engine lived for many seasons. That was the only time in the 30 plus years I’ve seen a resolution to a crank shaft thrust issue. So at best all I can really add is to scrutinize drive shaft length. The word was that the transmission in that car was fine. They just went through it and sent it back. So evidently it doesn’t work things over inside the transmission when this is the case. I’ve seen probably 20 or 30 engine come through the shop with thrust issues. Out of countless numbers of engines that didn’t. Just a shoulder shrug issue. Replace what needs replaced and send it back out. Outside of that one racing engine I’ve not known of another one that ever resurfaced for a persistent thrust wear issue. I will add that when you install that new crank check the thrust clearance without the thrust bearing main cap installed. Only with the upper thrust installed in the block. Note that thrust clearance number. Then after you know what the upper thrust bearing clearance is install the thrust main cap obviously with the thrust bearing in. I like to lightly snug down the thrust bearing cap. Say 15-20 lb.ft. of torque and use a soft plastic dead blow on the front and back of the crank. Give it a few good thumps back then do the same from the rear of the crank. I use a block of aluminum so I don’t tear up my dead blow hammers. Doing this will give the thrust main bearing cap a good chance and squaring itself up. Many engine builders do this. After that torque the cap down fully and check thrust bearing clearance once again. By doing this you’re identifying how square that thrust bearing cap is to the main cap saddle in the block. So obviously if you’re seeing a different reading with the thrust cap on you know that cap isn’t setting straight. Hope this helps out. You seem to be putting your due diligence in the right places with the information you have shared. Don’t fret over ball honing that block. I’ve tested cylinders with my Profilometer that had been ball honed only and it puts a very suitable surface in the bores. Take care.
WOW Hugh! I, as well as anyone else who comes to the comments section definitely appreciate you taking the time to share that info! Agreed I am fully expecting to find nothing wrong with the converter or trans, but atleast I will be checking them. Who knows how the truck was driven in the 290K miles before I got it but I will make sure its right and im sure it will be back on the road for many more years. Appreciate the tips and kind words!
You problem is the converter and front pump period, there are no horizontal forces in a combustion engine and therefore no need for added oil to the thrust bearing.
Appreciate your input. As I mentioned in the video, those are possible causes which I can only test for when the engine is back together and running in the truck. I will test them when its back together. Adding some extra oil flow to the thrust bearing cost nothing and doesnt hurt anything so why not do it? I believe in my case, low oil allowed the normal force of the trans/converter to push the crank forward and damage it. I could be wrong and if I am, I will find out with additional testing.
I am an automotive machinist. Been in the trade since 1990.
I had a thrust bearing issue in my 94 C1500 4.3 V6 4L60E transmission. Owned the truck since new. It developed an odd rattle only under acceleration right outside of the warranty.
Oil pressure was never an issue. Ran fine just that annoying rattle.
About 95K the engine developed a dead miss. One cylinder had low compression.
Made all the checks and discovered that a lifter was pumped up. Went in after the lifter issue. Drained the coolant. Got a little coolant in the oil so drained that out.
I decided to pull the inspection cover off of the transmission and it was then I realized the thrust bearing was gone. Those V6 engines had an external balance weight on the flex plate and that was the noise I was hearing. The counter weight was hitting the back of the block. It did that for over 40k miles.
Like yourself I had to try and figure out what the culprit was.
I towed a smaller jet boat. Nothing giant. Couldn’t tell you the weight. The truck never even acted like it was hauling a load. Still yet all the mechanics I did machine work for told me that hauling anything with truck should not be done in overdrive.
I did not know that.
Then came the ballooned converter story. I had it checked out. Nothing was wrong with the converter or transmission.
Took it to the shop I worked at and had the crank thrust welded and ground the crankshaft. All was like brand new.
I never figured out anything direct. Could have been the towing I’ve just seen others tow heavier in the same type truck and never have any issues.
Chalked it up to some times things happen and you don’t know why.
That rebuild lasted for another 200K with no thrust issues. My daughter drove it to school for a year or two. All the single mothers my wife worked with drove it while they were saving for car repairs.
Quite honestly I didn’t see the truck its last several years on the road. My niece was the last to drive it and called my wife to come get it.
It was tired and worn out and I bet the oil change intervals were sad.
One interesting issue surrounding thrust bearings arose while I was working for a machine shop that built very high end racing engines. Most for NHRA super comp dragsters. Several national title holders we built engines for. The shop had a great reputation for quality work.
On one particular engine the thrust bearing issue paid a visit. Chewed up a $2500 crank shaft just the same way you’re looking at. You don’t weld these cranks up and turn them. You buy another brand new crankshaft. This was happening rapidly. Normally performance engines have a two part warranty. Breaks in two pieces you keep both pieces.
In this case we had to do the work and buy the parts. It happened again. We asked the car owner to check this and that. “Ballooned converter”. Nothing doing.
Then the third time around another racer that was our customer was gracious enough to help out the engine back in the car and that’s when the issue was noticed.
It was a dragster with a four link rear end and a very short drive shaft.
The four link was not adjusted correctly forcing the driveshaft too far into the transmission Bellhousing.
The car owner was obviously sick. The very expensive two speed power glide had to be sent in for checks. The car was out back together and that engine lived for many seasons.
That was the only time in the 30 plus years I’ve seen a resolution to a crank shaft thrust issue.
So at best all I can really add is to scrutinize drive shaft length. The word was that the transmission in that car was fine. They just went through it and sent it back. So evidently it doesn’t work things over inside the transmission when this is the case.
I’ve seen probably 20 or 30 engine come through the shop with thrust issues. Out of countless numbers of engines that didn’t.
Just a shoulder shrug issue. Replace what needs replaced and send it back out.
Outside of that one racing engine I’ve not known of another one that ever resurfaced for a persistent thrust wear issue.
I will add that when you install that new crank check the thrust clearance without the thrust bearing main cap installed. Only with the upper thrust installed in the block.
Note that thrust clearance number.
Then after you know what the upper thrust bearing clearance is install the thrust main cap obviously with the thrust bearing in.
I like to lightly snug down the thrust bearing cap. Say 15-20 lb.ft. of torque and use a soft plastic dead blow on the front and back of the crank. Give it a few good thumps back then do the same from the rear of the crank. I use a block of aluminum so I don’t tear up my dead blow hammers. Doing this will give the thrust main bearing cap a good chance and squaring itself up. Many engine builders do this.
After that torque the cap down fully and check thrust bearing clearance once again. By doing this you’re identifying how square that thrust bearing cap is to the main cap saddle in the block. So obviously if you’re seeing a different reading with the thrust cap on you know that cap isn’t setting straight.
Hope this helps out. You seem to be putting your due diligence in the right places with the information you have shared.
Don’t fret over ball honing that block. I’ve tested cylinders with my Profilometer that had been ball honed only and it puts a very suitable surface in the bores.
Take care.
WOW Hugh! I, as well as anyone else who comes to the comments section definitely appreciate you taking the time to share that info! Agreed I am fully expecting to find nothing wrong with the converter or trans, but atleast I will be checking them. Who knows how the truck was driven in the 290K miles before I got it but I will make sure its right and im sure it will be back on the road for many more years. Appreciate the tips and kind words!
You problem is the converter and front pump period, there are no horizontal forces in a combustion engine and therefore no need for added oil to the thrust bearing.
Appreciate your input. As I mentioned in the video, those are possible causes which I can only test for when the engine is back together and running in the truck. I will test them when its back together. Adding some extra oil flow to the thrust bearing cost nothing and doesnt hurt anything so why not do it? I believe in my case, low oil allowed the normal force of the trans/converter to push the crank forward and damage it. I could be wrong and if I am, I will find out with additional testing.