my 54 truck has the torque tube driveshaft. The torque tube ball on the back of the transmission was shattered and needing replacement. This is a plate on the back of the trans that exposes two bearing races. I removed the 8 bolts for the plate on the back of the trans and removed the broken 1/2 circle piece for replacement. note: the other half of the torque ball is on the shaft and ok. once I removed this plate from the back of the trans the lower bearings and upper bearings and shaft is exposed. My issue is this.... while moving the trans around, the circular ball bearing races and upper shaft that comes out of the upper trans shaft hole in the back of the trans came out about 2". Ive tried everything to get the race back into the housing hole so I can put the replacement plate back on with no luck. the bearing races are the exact size of the holes they came out of and I can only get approx 1/4" in the hole but gears inside the trans seem to be holding me up from sliding it all the way in. So since the races wont seat flush no matter what gear or neutral or shimmying I try, I cant put the plate back on. I removed the top of the trans and the gear shift to gaze inside to see what the interference is but cant tell. Everything is beautiful in there and im sure theres a trick to this but im at a loss. So ive got a 4 speed on the floor with both rear bearing races hanging out of the trans housing and that is my issue. note: ive never taken these drives entirely out or as far as I can tell slid them out enough to slide them in against different teeth. How can I get them back to seated and will jocking around everything inside make it not sync or not be in correct gears? Ive searched and I cant find any diagrams or schematics to see where the hang up is.
Some of the roller bearings have dropped out of their pocket. You're at the point the trans comes out, all the parts cleaned & painted, & stuffed back in. The SM 420 is an easy trans to learn, and unless you have pitting or rust, probably needs only gaskets to be ready for another 60 years ... just read your Chevrolet issue shop manual and you can't go wrong.
The trans is already rebuilt, I have it on the workbench. I'm just trying to figure out how to cram it all back together. I've noticed I'm about half a tooth distance off on the two bottom gears that move w the lever on the side. If the last large upper gear gets the bottom lower hear meshed to it I'm close. And I don't have anywhere in a manual anything about manual transmissions.
Like GMC said, needs to come apart, the needle bearings on the main shaft are out of place and preventing the main shaft and pilot shaft from fitting together, only way to get them in place is to dis***emble the trans.
you can't just cram it back together. It's like one of those Chinese puzzles, it goes together only one way. http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm07118.html have fun
I have to agree with what 302GMC and Rich B said in posts 2 and 4. You have a needle bearing or two out of place that have to go back in place and the only way to do it is pull it back apart and start over. Those transmissions with different tail ends were run for a number of years and are still popular with some of the Jeep contingent. Here is one step by step photo page of rebuilding one like the one you have. http://www.pbase.com/dennygraham/sm420_rebuild&page=all here is another that may be somewhat better in that it has actual instructions. https://www.flickr.com/photos/advance-design_parts_co/sets/72157632620943718/
mr 48. thanks so much for the photos...much easier process w/ readable instructions. I only had xeroxed copies of xerox copies that were difficult to read.
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