Chevrolet C8 1940 Cab 11 restoration, The Netherlands

Alex van de Wetering · #1 02-02-17, 22:37

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 · #2 03-02-17, 01:23

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

Bob Carriere · #3 03-02-17, 03:27

HI Alex.

Those enclosed driveshaft tubes a much more avaialble here in North America and they regularly come up on Rbay as NOS stock.

Around here any young hot rodder who installs a large V8 in an old GM truck usually scraps the enclosed tube/driveshaft system as being too weak ofr larger engines.

I have a complete 1940 Chev one ton truck that has the complete power train. It is in bad rusted condition. Crawling underneath it has the same 4 speed tranny as a CMP...... left hand bellhousing clutch..... and fully enclosed driveshaft. It would not be difficult to replace the rear cover of the civvy 40 model with the open system of the CMP. A new driveshaft and suitable yokes and u-joints could be found to fit the new set up.

The ease of doing the conversion is demostrated by other C8 owners who have done exactly that.

Too bad the NOS parts here in North America are so heavy to ship overseas.

I would not trust the welded joint in your truck. To get your truck on the road you could do the conversion and at a later date if you ever find all the parts needed for the original set up..... replace the parts......to return to original set up. All of which can probably done from underneath the truck.

Good luck.

Bob C

cletrac (RIP) · #4 03-02-17, 05:55

The 40 to 46 pickups all used that setup. They also usually had a 4:11 gear ratio.

Maurice Donckers · #5 03-02-17, 07:59

Alex, the spider and yokes failed , we fixed it twice , and tried to beef it up in the tube , but there is no room , if you want to step up one size in U joint.

David DeWeese · #6 04-02-17, 20:55

I looked online and found that the u-joint "repair kits" offered by the Chevrolet parts vendors were said to fit '40 through '54 trucks with both 3 and 4-speed transmissions. Went to the shop today and pulled a u-joint assembly off a 1954 truck 3-speed, and also the front yoke from my busted original C8 4-speed transmission.

Sure enough, the u-joint from the '54 3-speed fit the C8 4-speed front yoke exactly. Both rear yokes are the same with 17 splines, but the front '54 3-speed yoke is smaller in diameter than the C8 4-speed one..

Alex, you are welcome to any of the parts in the photo, as I'll probably never need them...

Thanks, David