The Stovebolt Site Forums The Shop Area Engine Shop u joint problem???

Just rebuilt the Tranny (sm-420) and installed. On test drive under accelaration no noise, when I let off the gas and coast, I get a vibration and banging sound what I think is coming from the drive train. Feels like the u joint, also the problem existed prior to pulling the tranny.

How can I be sure it is the U joint? and if it is, do the rebuild kits work okay?

Thanks all.

can you just get under and feel and see how much play is in the ujoint? i am not aware of rebuilt kits for u joint, usually just bet a new one. 10 or 20 bucks for the ones i have done. good luck, hr

Check the drivelines to be sure they are in phase with one another. That means all joints must be at the same clock position, front to rear. Since yours would be a two piece shaft you must have a slip yoke/stub shaft in the middle. Not getting the slip yoke back in phase with the front is a common mistake and why it is important to mark the position when disassembling.

I think there is only one U joint on my 51 1/2 ton truck. Its an enclosed TT. Correct me if I am wrong??? thanks Money.

Yes, there is only one u-joint on a 1951 3100.

Yes, there is a u-joint repair kit for your truck and it fixes most u-joint looseness, except for looseness of yokes on splines.

Almost sounds like a rear end problem. If the U-joint was real bad you would have noticed when you were putting it together. Pull the cover off the rear end & see if the carrier is snug in its bearings.

could it be the bushing for the torque tube? I think that they call it the okie bushing?

I'll check that wrench, thanks.

Don, where is that bearing located?

wow, i didn't know those older style had a repair kit. course i haven't had a truck with a tourqe tube.

Dumb question time, looked at he exploded parts view in manual and dont see anything called a carrier.

http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0414.htm

What is the carrier?
Thanks !

I think the carrier is part 21 in that diagram. Here is another picture of it in that same manual. The ring gear is bolted to the carrier.

THe carrier is part of the rear end assembly. The ring gear is bolted to it & the spider gear assem. is inside. It should not have any side to side play but will have a small amout of backlash in the gears. Likewise with the pinion gear. The book probably calls it a differential carrier.

Thanks Wrench, that helps, Ill check it out.

Before you go much further. Remove your differential cover. Based on your symptoms, your pinion bearings have probably failed. Take a look at my webshots page and you will see what I mean.

thanks for sharing those pics. I will check there first along with the carrier, then move up the TT. Thanks all.

Hy 1951purney, the "carrier" is part of the differential, if you take the cover off the diff. as Wrenchbender Ret. suggests, you can check and see if you can move the "carrier" [the part that the crown or ring gear is bolted to] side to side. If you can move it, then your carrier bearings are worn, and the differential should be rebuilt. You can try to tighten the bearings up, but do not adjust the backlash tighter than the high end of the clearance specifications, that should allow the gears to run together without running on the wear ridges of the gears. This does not take into account any wear on the pinion bearings, or the "oakie" bushing, which is in the torque tube up near the transmission. How long a re-adjustment of the bearings will last is anyones guess, hope that helps.