I have a JDM LS tranny. Im on the highway one day and know that my 5th gear syncros are bad (keeps popping out) but decided to keep popping it back in. Finally the 5th gear pops out again but this time will not go into any gear at all!! So thinking its my pressure plate i turn off the car and noticed it wont go into gear even if the car is off... i bring it back home..take the shift linkage off and notice that the little rod it connects to will not push in..even by banging it with a hammer. I know its not stuck in gear cause without the clutch pressed in grinds in 4th.reverse and 2nd but doesnt grind in 1st..3rd or 5th... kinda like something is blocking it from moving in...any ideas??

 

You should be able to shift the tranny into a gear without pressing the clutch predal when the car is off.

I feel that it is not a clutch issue. I think something is wrong with the tranny internals.