Drive shaft support bearing breaking.

[steeeeeve]

Originally Posted by HO455

Please correct me if I have misunderstood you. You are saying the truck was a long bed coil spring truck to start and has been converted to a short bed leaf spring truck? I believe there in lies the problem. The carrier bearing you have is what I know as the 1/2 ton coil spring style. As you drive the drive shaft moves forward and aft as the suspension travels. The coil spring trucks have a limited amount of movement transferred to the drive shaft during normal driving, as the axle is bolted solidly to the swing arms. So GM used cheaper style carrier and driveshaft. (Shocking! I know.) This style of carrier absorbs that limited movement with the rubber surrounding the actual bearing. The leaf spring truck rear axles are subject to twisting as result the amount of driveline movement is greater. On these trucks the carrier is fixed and there is a slip joint in the rear section of the drive shaft to absorb this movement and keep the front half of the drive shaft steady. Your half breed set up means the carrier bearing is being forced back and forth as the axle twists under acceleration and deceleration. Your old carrier was probably well worn when the modification was done and had lots more slop than the new one. (Not to mention where the carrier ended up when the drive shaft was shortened) The new one with no slop still had to move so the mount flexed until it snapped. This problem occurs on bagged trucks that see a much lower and larger range of axle motion.
Photos show my old carrier and its replacement, a new drive shaft with the slip joint and fixed carrier.
I hope this helps. And as always my opinions are subject to peer review.

P.S. I believe that stsalvage's carrier set up is the C20 standard coil spring suspension carrier. Notice it has a slip joint adjacent to the carrier. It may have come on 1/2 tons with HD suspension. Another mystery we will never know the answer to for sure.

I'm way late to this discussion, but i've experienced a similar problem. recently acquired a 68 shortened c10. the cb broke on me then the second one broke after about 50 miles. I just finished installing the heavy duty cb and the slip shaft sold by cj pony parts. Pretty much the same setup in this post. Looks like it should do the trick. fingers crossed!