Today I installed a ford factory rebuilt 3650 transmission, a spec stg 1 clutch, and a mgw shifter. Install went fairly smooth and while taking the car out for a drive after the install I notice the car won't stay in 3rd gear. Shifts into 3rd smoothly without any grinding at all however after a few seconds it pops into neutral. This is my 3rd clutch install and I'm puzzled as to what's the issue. Any ideas?

 

First of all, did you use the shift stops in the MGW shifter?

If you did, there is a chance that you didn't set the set them correctly and 3rd isn't engaging fully. Try backing them a turn or better yet, just remove them. The 3650 trans doesn't really need it.

 

Shift Stops were not used.

 

It may be that the detent pin is not moving freely, or the spring is weak--IIRC the center one is for the 3-4 shift rod...



Remove the cap and use a magnet to fish out the spring and detent pin...