39-45 GM 590474 GKT-134 Crash Box/How to Shift...

[philipj]

Does anyone have experience shifting the GKT-134 crash boxes fitted to pre 1947 Chevy trucks? What is the best rpm to shift them? If they cycle through all gears with the engine off and with the engine running are you safe regarding condition despite being hard to shift while moving even if you double clutch? Driven  a lot of vehicles before, but never one with a fully non-synchronized gearbox... I must be doing something wrong...

Edited January 6, 2019 by philipj (see edit history)

[Isaiah]

How is the oil in the tranny .it takes some driving to get the nack of shifting them,

[Guest]

There are lots of videos on You Tube.  Look under "floating the gears".  Then it is simply, practice, practice, practice.  I usually only use the clutch when starting from a stop or stopping.  normal driving I float the gears.  If traffic is heavy and in a hurry I double de-clutch.  After 59 years and 400,000+ miles on my daily driver I don't even think about which or how, I just drive. Trucks and cars are different but an unsynchronized transmission is an unsynchronized transmission.  Normal driving I would shift  to second at or below 5 mph and to third at or below 10 mph.  If I want to keep up with modern traffic then I go into second at 15 mph and third at 25-30 mph.

I am not familiar with your GKT-134 but if it is a four speed first is probably a granny gear and should only be used starting uphill with a full load.  I have driven everything from my car up to a 16 speed road ranger, including a 1934 Diamond T, 48 Reo, 54 White and on up through 4 and 5 speed with a 2 speed rear end, a 5 and 4 transmission and almost all the itterations in between.  Floating the gears is floating the gears.  Practice, practice, practice and of course the right viscosity gear oil.