Hey guys I tried searching all evening for this issue in having but unfortunately I couldn't find anything that really helped me or sent me in the right direction. So the chain of events are as follow:
I was getting on the freeway earlier today and got on it in third gear. As I was shifting into fourth I felt and heard a grind and then all of a sudden it wouldn't go into fourth. So I tried going into fifth and it did it just fine. Now, I drove it all the way home and tried to trouble shoot by driving around the block. I noticed it will not go into third and fourth sometimes, but other times it will. I checked my shifter cables and they seem to be moving just fine. Everything looks normal to me. It just won't go in sometimes. Any info will help, thanks!

 

Hey man have you noticed if it does it under boost or high RPM? When trying to shift into those gears. I had same issue last year with my transmission third gear would go in under 3k no boost as long as i was going less than 30 MPH other wise it would grind hard and lock out. Also my 4th gear would be hard going in under full boost, i would have to slam it in, no grinds just hard. I had my transmission rebuild by shep i have a bent shift fork and bad synchro for 3rd.