One of my co-workers posted this question to an e-mail list that I subscribe to (as does Nate). I noticed that there have been no responses, so I thought I'd post it here and see what this forum thinks is wrong with her SM-420. My 59' GMC 100 pickup has been driving great for about a thousand miles since I put in a new clutch. Then, yesterday, with no warning, the gear shift lever (four on the floor) got stuck. The truck is in 1st gear and the shift lever moves somewhat fore and aft, but it no longer moves side to side at all. The clutch works as normal and there's no grinding, the transmission is just stuck in first. There wasn't even an alarming sound of any kind when it got stuck, I was just pulling out of a parking space when it happened and everything was normal until I couldn't upshift. I pulled the shift lever/linkage attached to the tranny top cover off this afternoon, and that appears to be where the jam is. Even with the cover off of the tranny, the shift lever is still jammed. However, I don't see anything obviously broken, frozen, or terrifyingly worn on the linkage. Certainly I'm not seeing anything that looks like it should have caused such an immediate and complete malfunction when all has been great for years. Has anybody seen this before? Any thoughts would be appreciated, I'm finding this a bit perplexing. Thanks! Heather
Novak Bill, You might refer Heather to Novak Conversions. These jeep guys are searching the world over for our sm420's to put in their rock climber jeeps. I bet theycan help, they do extensive tranny work as well as converssions. They have been helpful on the phone with me, just search "sm420", they will pop up. Jim
I'll go out on a limb here... Something broke. Probably a Jesus clip or ring thingy. It would be neat if it was just the retainer that held the shifter in place had a tab rust through and let the shift lever go out of whack to where its shaft didn't work like it was supposed to... Wait a minute. I just described ~ never mind... That's why I never "pipe" up on issues like this... Let me just say, "Good luck!"
I didn't see it so I didn't respond to it . There's not a whole lot that holds the big sliding 1st. gear into place so once the lid is off I'd take my long flatscrewdriver and gently shove it & see what's what . Failing this I'd tear it down , they're about the simplest tranny I've ever been inside of ... can't be much wrong with it .
shifter Just a guess, there are two pins, one either side of the shifter, near the top that the shifter pivots on, mine were badly worn and loose, possibly one of these has snapped off and got jammed in the linkage or shifter has twisted and jammed.
