Have a mid sixty,s M - 22 that sticks in 4 th gear once the car is driven about 10 or 12 miles , I have had it in and out trans shop 3 times still same thing . It will shift fine when cold in and out of all gears . But once it gets warm it hangs in 4 th . I have had a lot of 4 speeds over the years , never had one do this ! Anyone have any ideas ? Shifter and linkage are good and did not have this problem to begin with ! It was making roaring noise in third , decided to just have rebuilt , all new bearings and sychro,s , gaskets and main shaft ,