'51 GMC 3100, stock engine and trans, three speed column shift. I drive the truck up and down the street today and the shifter started getting tight and wouldn't shift out of third. I limped it back to the shop in third and started taking things apart, starting with the selector box on the column. There a lot of slack between the two u-shaped cogs and the selector had squeezed past the cogs to the outside. So, that explained what happened up now the selectors on the gearbox are stuck. I drove it back in third gear so I don't know how they could both be stuck, but I'm not familiar with the gearbox. The rods are disconnected and both selectors are frozen in place. What should I do next?
If you can get the vehicle in a position where there is no tension on the gears from the drive shaft you can manually move the shift selectors to the correct position. Do this with everything hooked up and on the column under the hood. Mine did this few times after I first got it. I would pop the hood, move the shifter rods to the neutral position and everything would be alright, for a while. As I said, it did it a few times when I first got it but has not done it again in the last 2 years? I am not sure what I fixed or changed that corrected the issue.
Thanks for the reply. I did jack up one wheel and move the driveshaft back and forth with no success. I guess I'll try lifting the whole back of the truck just to make sure and make it a two person job.
Assuming I get the gears to release, what's the best way to tighten the selector mechanism? Everything seems fairly good with no obvious wear on most pieces, except that the distance between the cogs allows the selector bar to squeeze between them and end up outside the "box" the cogs make. I'll add a photo later today. Can you shim behind one of the cogs/jaws to make them closer?
Okay, I got the gears free. I got both rear wheels off the ground and had my son move the wheel to create slack in the drive train and still couldn't get the selector to free up. Ended up taking the side cover off where the selector arms are and had to jostle the gears around quite a bit to get them loosened up. Now I need to fix the selector box tolerance.
What's the best way to tighten up the distance between the cogs so the selector can't squeeze between them and end up in the outside?
Grease Monkey, Moderator General Truck Talk & Greasy Spoon
I can’t tell from your photo where the shift arms are in relation to each other. With the transmission in neutral the arms should line up perfectly with each other. If not take the rods off and turn the fittings to line up the arms. Makes shifting smoother.🛠
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Just drove the truck again and it works great now. I've read how you're suppose to shift the column shifter, "H" pattern and all. How I described it to my son is that you shift into gear, then shift out of gear, then shift into gear, then shift out of gear. Basically starting over each shift. That slows you down and it works good.
Kinda glad it got stuck in gear, made me fix it instead of learning how to adapt to it.