I called and left him a VM
the manuals are usually strong and start popping out of gear when worn out.

I am betting its the linkage or mounting. We replaced all that stuff on our car. He could cut an access hole on the passenger side of the trans tunnel. Start at the shifter and go about 4 inches forward. this way he could see the linkage. If the car will not go into 3rd or 4th Im guessing the shift rod isnt able to pivot. IF it can go into 4th but not 3rd then Yea its the trans..

B