I'm playing around with a '93 ZF S5-42 which... won't go into reverse. Just plain grinds. However... If I pull the shifter off the top, and manually stick it into gear using a couple of screwdrivers to lever the "socket" piece... it'll go and stay in reverse. It's like it won't go quite far enough with the shift lever. All other gears work fine. Any ideas on what might be worn out or missing to cause this? (Note: I've got no history on this trans. It was found in a JY on top of a stack of junk, missing the shifter. Got it really cheap because of that).