I have a 1990 YJ ......and one morning as I backed it up it acted like it ws in 4 wheel then after that moment from then on it has not been able to shift into gear without being at just the right speed.............is there such a thing as the syncromesh part of a tranmission seasing to operate ? my e-mail is squiggles25@hotmail.com

 

Possibility of low fluid, or input and output shafts have welded themselves together.

 

it might be the problem of improper engagement of clutch with driven and driving shaft nad lower levels of lube oil..............:):):)