The Stovebolt Site Forums The Parking Lot Big Bolts CCKW 5 Speed and 5.43 third members/rearends 1.5 tons

This is going to be a mouth full. Got a 52 chevy 1.5ton and a 46 gmc 1.5 ton. Curious if GMC ever had the 5.43 - 1.5 ton rear end in that year or if a newer chevy third member could be swapped in.

The 46 gmc has the crash box, will the cckw 5 speed bolt to this bell-housing? The crashbox had a different bolt spacing and a smaller center hole compared with the SM420 which is what the 52 chevy has.

Thinking about swapping both trucks over to the overdrive cckw 5 speed and 5.43 rear gears.

Both truck have just the 4 speed with the 6.17 geared rear ends. Just thinking of a way to increase much needed speed while keeping the old wheels and tires.

I don't know much about the civvy side, but the 1.5 ton G506 4 speed will bolt up to a 50's 235 bellhousing. If the G506 4 speed will bolt up, the 5 speed G508 CCKW tranny will bolt up, but 'fitting' is another matter. I'll post some side by sides of both for reference.

A TON of people talk about putting the CCKW 5 speed in a lot of 40's 50's trucks to get that overdrive... but I've never heard of it actually working or even being done. It's possible, but the 5 speed is a monster.

I drove my CCKW for a short while before tearing it down, not the best for gaining more speed I would think. OD seemed like 3rd gear in my 2 ton. I realize my gearing was insane but 45 mph max in OD did not impress me. I put in a complete 1970's 292 with 4-speed out of a 2 ton. I have not driven it yet but in theory it should do 50- 55mph with 8.25 x 20 tires.....just my take on it.

I think your CCKW has 5 on 8" bolt pattern, doesn't matter what it is, I made somewhat easily(if my labor doesn't count for anything) wheel adapters to go from 8 lug D 70 rear end(could be done to GM 14 bolt, etc.) to 5 on 8 for my KB-5. GM 14 bolts are plentiful and inexpensive, have lots of ratios available, come in singles and duals. D 70 an D80 would work also, expensive, though.

A stock CCKW drive line is not made for speed, and the governor will limit engine RPMs (and can be easily removed).

The truck will go 50MPH plus... the placards for max speed are for a different era.

But many people think the overdrive is really much more than it really is. The book puts the OD ratio at .799:1 so if you have a gear ratio calculator you can plug that number in.

What are the rest of the gear ratios in the CCKW 5 speed with overdrive? Thanks. Jim

The CCKW used a Clark 204VO transmission which was a sliding gear transmission. That means no synchros in any gear. The ratio was 6.06, 3.50, 1.91, 1.00, 0.80 with about a 6.00 Reverse. The shift pattern was rather awkward too.
2 OD R
3 4 1
Having reverse above 1st was good for when you got stuck. You could rock the vehicle back and forth from 1st to reverse. I would recommend you try to drive a sliding gear or spur gear transmission before you go any farther with plans.

Your ratios are a little off.. did you round them?

R 6.00:1
1 6.06:1
2 3.50:1
3 1.80:1
4 1:1
5 0.799:1

Source: TM9-1801 10 March 1944 page 38

I did round the OD. I probably just transcribed 3rd gear wrong. I was looking at a chart with a lot of numbers. I did round the OD. But the rest of it is correct. And Clark 204VO should bolt right on to his 1946 clutch housing , but not on his 1952. I have a 1946 GMC 1 1/2 ton with the 4 speed. A previous owner replaced the 236 with a 302, which it really doesn't need. I have 3 550 GMC's with 370 V8 engines. I drove a 550 80 mph down hill 50 years ago. I don't care to go that fast any more in an old bucket of bolts. But I do still drop of of hills 80 MPH in our Cummins powered Internationls. The speed limit on IH 10 here is 75 and they overlook 80.

The only stock motor I have is the 270, the rest are all mixed matched.. but I'm pretty sure that if the G506 4 speed bolts up, then the CCKW 5 speed should. I have a 58 235 with a civvy motor and bell housing (by cast in part number)that will fit a G506 tranny, so that should also take a CCKW 5 speed.

Now if it will match the frame/linkages is another matter. The 5speed is HUGE compared to the 4... so while the bolt pattern may fit, the actual transmission fitting may not.

Its to cold in the garage to make 10000% sure, but if it gets warm I may set one up just to show the sizes.

Thanks. I'm looking at purchasing one of these 5 spd overdrives for my 50 GMC 450 firetruck, which has a Clark 5 spd already. This is healping me out as well.