Chevrolet C8 1940 Cab 11 restoration, The Netherlands

[Alex van de Wetering]

It was about time to spend some time on the driveline of the C8......starting with the transmission and slowly preparing to move to the engine.


I removed the transmission from the engine and chassis some years ago and it was patiently waiting ever since. It was hard to even see the actual transmission through all the layers of dirt, oil and grease. The gear lever was pretty much seized, as well as the small lever for the reverse gear. I had already treated some of the parts with penetrating oil, but even then the gear lever hardly even moved.

After removing all the grime, from the exterior of the box, I was able to remove the universal joint and the gearbox cover/shift tower with the gear lever still attached.

Inside it wasn't looking all that bad....and it even had some oil in it. The sliding gears however were seized to the shaft.
As you can see in the pictures, a previous owner added and extra lever and additional shaft… probably to drive some sort of wrecking gear. With help of Frank von Rosenstiel I have since found out my C8 was used as a tow vehicle in a Toronto used car lot, before ending at a farm vehicle in Pefferlaw, Ontario.

The extra gear and shaft were easily removed…and after liters of penetrating fluid, some heat and some gentle persuasion, the sliding gears moved again and I was able to disassemble the transmission.

Alex

[Alex van de Wetering]

Some years ago I bought a spare civvy 4 speed Chev transmission from the web, but never looked at the internals of the box. So, now was the time. Both transmissions boxes were disassembled and after cleaning everything I started comparing the parts from the two. At first everything seemed the same, but than I found out the sliding gear of the spare box had one more tooth than the one from the original box....and I found out the main shaft of the spare box was slightly shorter than the one from my C8.

The bearings in both the original box as well as the spare proved to be in good condition, but sadly I found out the mainshaft front bearing (the cage one with the long needles) in the original box was gone....I only found a bunch of the needles....and, after close examination, one end of the bearing cage. Sadly the lack of a proper bearing, meant the inside of the main drive gear was very beaten up, as was the end of the main shaft.

After checking the parts manual I found out all CMP 4 speeds use the same main shaft....even though the u-joint setup of the C8 differs from it's bigger sisters. Tracing the partnumber in a master parts list, I read that it was supposed to be 10,5” long.....a 11” main shaft is also listed, but not used on CMP's. To cut a long story short, it seems the main shaft of my C8 box was replaced at some stage for an 11” replacement. The spare box had a 10,5” shaft....and above all the end of the bearing surface on the end of the shaft was in good condition, so I used that one....combined with the spare main drive gear ......and selected the best parts of the two boxes to rebuild the gearbox.

Alex

[Alex van de Wetering]

I am hoping one of the fellow C8 owners can help me out on the following.....I can't figure out the universal joint!

After cleaning the grease from the parts I found out my C8 has a mismatch of yoke and spider, and some things are welded to make it work.....I have a feeling the rearmost yoke that attaches to the drive shaft is the original C8 part....and the front yoke with gear for the speedo is from something else.(?)....but I am not sure.
I have checked the parts manual, but I haven't been able to find the parts numbers in the master parts list. So, basically....before I can start searching for the correct parts, I have to find out what they actually look like! Anyone have a picture of the proper joint???.......the C8 setup is not shared with C15 or any other of it's sisters.

Another thing I wonder is if I have the proper “trompet” shaped "ball collar" that protects the U-joint from the outside world.......it has the remains of a seal at the rear end, but it doesn't seem to have a screw-on cap as I have seen on other (civvy) examples.

Alex

[Mike K]

Alex

I can help you

The C8 uni joint and drive shaft design , is from the USA 1940 1/2 Ton pickup with 4 speed gearbox . The 4 speed gearbox was an option on the 1940 1/2 Ton pickup, you could order either a 3 or 4 speed gearbox.

My uni was broken, it seems to be a weak point in the driveline. Maybe Jim carter can help you.

[Maurice Donckers]

There was a guy sometimes traveling with me to shows with a C8 , even after renewing the u joints and other hardware , it still smashed to pieces . I solved the problem by putting a C15 rear end on the gear box and a modified C15 ordinary prop shaft behind it , and deleted the prop in the tube system .
After that he drove years around trouble free.
So maybe also an option for other C8 owners.

[Alex van de Wetering]

Mike, Maurice,

Thanks for your replies. So, that means we have at least 3 C8's with a U-joint that failed. Do you guys remember which part actually failed? the spider maybe...or the front yoke?

Thanks for reminding me Maurice....I couldn't remember who told me about the C15 upgrade!
Based on both your experiences I am now also looking at upgrading the U-joint. I am hoping to find something that will work with the tube and ball collar.

Attached is a picture that Andrew posted some years ago.....based on that picture I think my C8 has the original rear yoke, but had the front yoke and spider replaced.
My front yoke seems to be of a heavier design than original, so maybe I can save the it after cleaning up the welds and finding a spider that does work with both the front and rear yoke.
Another option would be to replace the complete joint for a heavier example, but than I would have to find one that has 17 splines to fit the C8 prop shaft.....so far it seems only Passenger Chevs and 1/2ton trucks at the time had 17spline shafts. I am also looking at GMC CCKW parts as they seem plentiful and cheap and they are probably a lot heavier than the C8 parts.

Thanks guys,

Alex

[David DeWeese]

Hi Alex,

Took some photos today of the joint assembly that was originally on my C8. If you want I can remove the yoke on the transmission and see if there are any part numbers..

Thanks, David