Ok, I’m pretty sure I’ve finally got it figured out, right down to the fact that the shop manual doesn’t really show Group# 4.318 Part# 606667 (Mainshaft Rear Bearing Retainer) for a 4-speed with torque tube driveline.
½, ¾ and ¾ ton special trucks generally came with synchronized 3-speed transmissions (2nd and 3rd synchronized). These were torque tube setups that we’re all familiar with.
You could also get a non-synchronized 4 speed transmission for ½, ¾ and ¾ ton special trucks with torque tube drive. This same 4 speed came in the ¾ ton long Wheelbase and all 1 ½ ton trucks with one major difference: when it came in these trucks it was set up for Hotchkiss drive (open driveline with an oil seal and Mainshaft Rear Bearing Retainer). This setup is what’s illustrated in the shop manual.
When the 4-speed was used in ½, ¾ and ¾ ton special trucks it was setup for torque tube drive, necessitating the addition of a different style of the Mainshaft Rear Bearing Retainer as noted in the text of the shop manual.
That is the mystery part I’ve been trying to figure out. It’s a pretty crude part, but I notice in my parts manual that it only cost 10 cents, so there obviously wasn’t much to it.
These are my conclusions. What do you folks think?
