I have the 3/4 ton truck, which is set up with a short torque tube like assembly, a carrier bearing, and then a conventional driveshaft connecting to the rear end. It is illustrated on page 4-29, figure 59, of the 1942-1946 Trucks, 1942-1948 Passenger Cars Shop Manual.
The transmission is the four speed, non synchro, original equipment unit.
I bought the truck with the knowledge that the transmission was on it last legs, drove it home and parked it.
We pulled apart the transmission, found the input shaft bearing, output shaft bearing, and pocket bearing were all shot. At some point in the past, a poor clutch job (failure to align the clutch disk with pilot bushing) caused the pilot bushing to get pushed in too far, thereby causing the input shaft to wander, thus ruining the transmission bearings.
Upon replacing these, it was time to look at the intermediate torque tube style drive shaft. It has a bushing, a bearing, a seal, a pair of retainer clips for the bearing, and a rubber vibration damping piece between the housing that attaches to the frame and the bearing housing on the tube.
I understand now that the one ton and larger trucks have a short drive shaft, not this short tube assembly. Had I known, I may have just sourced a transmission with an exposed rear u joint yoke (mine has a bushed u-joint, bathed in oil, familiar to all with full torque tube cars and trucks). I would have had to get a carrier assembly and intermediate driveshaft (which would need to be shortened).
I could then have avoided the following:
Sourcing a Bushing (via Ebay) Original GM part #596907.
Sourcing a Seal (National #471192)
Sourcing a Bearing (Koyo #6207 2RDC3)
Sourcing a Snap Ring (Waldes #5100-275) The large snap ring, the small one was fine.
The rubber damper is out and being measured for replacement. I can't find one. It looks like I am going to have to go the two part urethane route, and pour my own, depending on cost vs. having one made up. If anyone has the original GM Part Number for this rubber piece, let me know!
Chev's of the 40's also carries the bushing. The 3/4 ton is beefier than the 1/2 ton, and parts are more scarce.
I will keep you posted, I have yet to press the bushing in, and the damper is going to be an issue.
The old bushing was a piece of cake to remove, having been worn thin over the years.
Hope to have the beast on the road in time for the Greenwood Car show on June 28th.
Hope this helps someone with a bad intermediate driveshaft/tube on a 3/4 ton. You now have enough information to get it functional again.
Zeb
