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I have a 51 1/2 ton that has aquired a 56 engine. It still has a torque tube driveshaft. The 3 spd trans dosen't shift well - syncros, I guess. Could anyone tell me how to determine if the trans is the 51 or 56? Or does it matter, ie, are the same syncros used in both years?

A 1956 transmission would not be torque-tube. It would have a long tail piece with a splined shaft and an exposed u-joint yoke. I don't know about synchros.

Thanks Frank50 - maybe you can help me further - I took the side cover off the trans .. All gears and teeth look good... I didn't see any small gears that look like syncos that I'm used to, only one large sliding gear and some other large gears on shafts... if these gears all look ok, how can I tell if I need to replace any? I've not run the trans - the guy I bought the disassembled truck from told me it had some problem with shifting. Any suggestions? Thanks for your help. No one near where I live to talk to about these trucks.

Gobs, sure it wasn't just shift linkage problem hanging up and stuff. That happens quite a bit on these old trucks. Bet with a better clutch adjustment and linkage repair, you'ld be fine. Or, good time to put in a later trans, like a 4spd from same era with open driveshaft and newer rear. As long as it's in parts now anyway. These old trannies weren't that good. 1st was non-synchro in them too, not like it is in newer trannies.

GL - Thanks for the reply ..I took another look at the linkage and it was pretty loose and worn, I believe I'll try fixing that and reinstalling in the frame. Maybe then I can see how it shifts before I get too far along with the cab, In case I do have to change it to a 4 spd. Thanks again!

Gobso,

All the three-speed trannies had unsynchronized first gear up until 1967 (?); first in my '64 C-10 was still un-synced, anyway.

If the bushings in the shifter linkage are worn, you can have a real hard time shifting- the usual symptom is for the trans to be in second while the column lever looks like it's in "neutral", and won't move from there. This usually happens at an intersection during heavy traffic with the truck headed up-hill and the only cure is to shut down the engine, set the parking brake (or brick ,whichever is in working order) and getting under the hood and grabbing the shift rods and working them around until things unbind and the tranny finally goes into neutral (usually accompanied by a symphony of horns from surrounding cars!).

At any rate, "any" 1948 to 1963 three-speed will bolt to the bell housing; the output end is another story. All pre-'54 3-speeds up through 3/4 ton had an enclosed (torque tube) type universal joint at the rear of the tranny.
1/2 tons had the torque tube all the way back to the differential. The 3/4 tons had a short "torque tube" back to the center carrier bearing, then open back to the differential.

1955 and later transmissions had the long extension housing w/ the fine splines and slip-joint on the rear tranny shaft.

One other thing, my '54 began to be really difficult to shift into first gear: turned out to be a collapsed front cab mount, which allowed the cab to "slide down" the steering column enough for the first/reverse shifter lever to hit against the bottom of the toe-board, so make sure your cab geometry is ok too.

Good luck!

Frank 54

Frank

Our 64 C-10 did have synchro first gear behind a 230. Best thing since sliced bread. Too bad I rammed a Caddy in 71.