VW Transmission Rebuild - Gear selection?

Problem: VW transmission "A" is popping out of fourth. I have another damaged transmission "B" with good gears that I'm going to use in the first transmission "A".
Should I use the primary shaft from "B" with all the good gears (including 4th), or push the gears off the shaft and put them on the original shaft that came with transmission "A"?
Check out my electric VW bug project at: /www.corbinstreehouse.com/PlugBug
Update: Here's what I did: • 1969 VW Bug Transmissi...
And back together: • 1969 VW Bug Transmissi...
-Corbin

[@mstile002]

They do that to the syncros on vw when they rebuild them it’s a trick I guess from day one the trans will only use 9 teeth if you rebuild the trans and see that the 9 teeth are badly worn you can grind them down and the trans will run on a different set of 9 teeth I know you posted awhile ago hope this helps

[@CorbinDunn]

Mstile00 thanks! I eventually got that figured out. I swapped the entire set and kept the same ring and pinion. It seems to work okay, but has a bit of a higher pitch at high speeds.

[@mstile002]

Did you check the pinion gear it maybe loose it’s supposed to be torqued to 150 ft lbs just a thought

[@CorbinDunn]

Mstile00 that’s a good idea - I have a transmission with the 4 bolts and not the center but style. I torqued the 4 bolts down to spec according to the Bentley manual. Next time I take it out I’ll double check them. Thanks for the tip

[@knockout818]

the 4th gear you had, was it with splines or keyed? thanks

[@CorbinDunn]

I don't think it is really either; it attaches with the synchro, and the synchro is what engages. ...Or what do you mean or are trying to find out?