Stovebolt.com Forums The Shop Area Driveline Driveline or suspension

I can't tell if the issues is tires, suspension or my driveline. I have been test driving my new 47 project truck after it has being off the road for over 20 years. It is now running good. Engine, clutch and 3 speed transmission all seem good. Here is what I need some help with. i am not sure what to check. While going down the road the truck seems to run fairly smooth. When I am either decelerating or just push the clutch in there is very noticeable high speed vibration. The second the clutch engages it stops unless I am braking with the engine. If that is the case I notice it but not as much as just coasting with the clutch in. My first thought was an out of balance wheel but the fact it seems tied to what is going on with the driveline has me baffled.

If depressing the clutch makes the vibration come and go then it's not the tires.

What make and model is your '47?

Mike B

Does that year truck have a carrier bearing between the transmission and differential?

It does not have a carrier bearing. 1/2 ton

I can't seem to pin this down. I guess my next step is to check the rear end. Not sure what to look for. I hope I know it when I see it.

I would guess one of the u-joints has some play and when the drive load is removed it can shift around, under decelleratoin with the clutch engaged it shifts out of position but doesn't shift around.

I would place the truck on stands and run the drivetrain. With a hand from someone else you could engage and disengage the clutch while watching the driveshaft and ujoints, you can also check the rear end.