I bought an S4c trans from a guy for a good price & he told me it has a bad diff bearing in it but goes into all gears with no problems. My question is should I just swap out the bad bearing or should I swap in a ITR diff. Also if I do swap in an ITR diff would I have to change any internals to make it work?

 

Supposedly a S4C is already a ITR transmission. An ITR transmission uses a larger differential like the GSR. The B16 and B18 LS use a smaller differential. Bad bearings wouldn't show themself with the transmission out of the car. Change the diff or the bearings and while you're at it, check out the gears and synchros.

 

s4c is a b16a2 tranny out of a em1

 

that is true.....it shares all of the same gears as the ITR tranny and has a different differential as mentioned above