I just had my trans pulled and rebuilt to the tune of 800$ clams. Since the rebuild it's like the third gear syncro's don't mesh. They guys at AA beep beep MCO (aamco) tell me that it is part of the breaking in period and it should go away by the next oil change or near 5k miles.
Any one ever heard of this?? And when will I be able to pull hard into third gear?

 

nope never heard of this. every transmission ive rebuilt, personal or customer has never grinded a single gear with new parts. maybe aamco only replaced the synchros themselves and not the corresponding hub like they should have? see if your receipt gives you a break down on the parts that were used and list them here.

 

^^^ I agree. Never had grinding with new parts.