The GMC CCKW

Chevy factoid:

The original WW2 Chevrolets use the standard civy tranny minus the spedo adapter. Later they changed the 1st and rev gear ratios to make the transmission have more of a close ratio rather than the normal granny 1st gear.

OLD 7.23 for 1st 7.15 for rev
NEW 7.06 for 1st 6.98 for rev

You can tell the transmission by looking at the counter shaft. If it has 2 grooves machined into it, then it is a close ratio one. Rev/1st gear and countershaft CANNOT be mixed. So that means 3/4 gear and the input shaft w/gear and the output shafts are the same.

Chevrolets, even the civy ones tended to break axles back then and with an additional 1.94 x 1 transfer reduction, it only got worse. I believe that this was at least part of the reason for the change.

But the transmissions interchange, and many Chev 4X4 now have either. If the owner is a good combination of man and machine, there should be no problem with snapping axles.

They do interchange. My first 2 close ratio tranys were junk doe to water going down the shifter shaft.

I now have 3 good close ratios ones. One will go into the K51 panel because it will be towing the K52 trailer (1 ton ben hur w/ PE95 [1500+lbs]in it)