Hanger bearing with suspension drop
 

Hey I'm looking for some feed back on my hanger bearing issue. 1970 GMC 1/2 ton, 350 engine, TH350 transmission, 4" rear drop springs, 2 piece drive shaft with solid rear (no slip yoke on rear shaft) and a clam shell style carrier bearing. I current have the transmission out at the moment (fresh rebuild) and noticed the bearing is shot. To be clear it separated from the shell. I've got a new one along with new u-joints on order. The old bearing was completely seized on, and i had to cut it off. After i got the old bearing off i noticed 2 things. 1- the front "horn flange" (i assume is to keep dirt out) had indentations consistent with internal cage/retainer of the bearing in it, and 2- the washer that keeps the rear yoke (front shaft) on was basically embossed to the pattern of the splines. Both telling me that there was extreme force pushing the carrier bearing forward, until the clam shell broke, finally relieving the stress on it by separating itself from the chassis. Now I've read many past posts on this issue, and the consensus is that the rear end moves forward approx 1/2" forward with a drop like mine. Other members have commented to switch to 1 piece drive shaft, made in China bearings, weld gussets to strengthen the housing and other say they blew the pinion bearing etc. My thoughts are to drill out the rivets that attach the bracket to the cross member, and re-attach it with about 1/2" spacers or washers to move the bracket forward to compensate for the forward movement of the rear end. The side effect of this would be the slip yoke in the transmission would go in and extra 1/2"? Has anybody done this? It sounds like a simple fix? The other alternative is take to a drive line shop and get the rear shaft shortened 1/2". Thanks!

Re: Hanger bearing with suspension drop
 

Your driveline is not correct. You cannot run a fixed shaft between the carrier bearing and third member. Even if you adjust the bearing to take stress of it while static. The rear axle moves forward and back as suspension cycles. This true on both leaf sprung and coil (trailing arm) suspensions. A fixed shaft can be run between the carrier bearing and transmission. There should be a slip yoke on the rear shaft.

Re: Hanger bearing with suspension drop
 

Exactly this, you need a slip yoke on the rear shaft. Contact a local driveshaft builder and they will provide you with a sheet of all the measurements they'll need to build you a new shaft. Or drop off the truck with them to have one fitted, either a one-piece or two-piece with slip yoke will work. With a one-piece, you will likely need to remove the carrier bearing support.

Re: Hanger bearing with suspension drop
 

Can you post a picture of both shafts including a clear view of the ends? When I saw this pop up again I was just thinking that maybe the unit was reassembled incorrectly when joints were changed? IDK, just a thought.

Re: Hanger bearing with suspension drop
 

Actually the OP is correct. My 67 had the exact same set up in it. (See the less than optimal photo) As far as I can tell the base 1/2 ton trucks came this way. The rubber mounting of the carrier bearing absorbed the back and forth motion of the drive line as the axle travels up and down. The only sliding joint in this set up is the yoke at the transmission.

The OP is on the right track with his idea to move the carrier bearing. When the truck left the factory the bearing was in a neutral position in the bearing mount with the rubber centered with the truck at ride height.

When the axle travels up and down the rubber flexes forward or aft though it's designed range of movement.
When the truck is lowered (Or raised ) this forces the bearing's rubber mount to move beyond its designed range of movement. This results in the rubber tearing off the bearing or the carrier bearing mount starts flexing until it fails.

When installing a carrier bearing the truck must be at ride height (No using the 2 post lift for this job)and the carrier mount must bolt to the crossmember without being pulled or drawn into place by the bolts. That allows the bearing's rubber to be centered or neutral and have sufficient range of movement.

The other issue I've heard of is that the replacement bearings available today don't have the same range of movement that the original GM ones did but I've never seen a side by side comparison of a NOS carrier bearing with a modern repop. It wouldn't surprise me if this were true.

To the OP I would do as your planning and when you've got things bolted up remove the springs and then do a range of motion test. Find some way to verify the carrier mount is not flexing and that the yoke isn't bottoming out.

When I needed to replace mine I converted to a billet bearing with a sliding joint in the rear shaft. The reason being that my Burban was on air bags and there is no way to find a reasonable neutral position for the factory carrier with the larger range of motion that a changing ride height that being bagged causes.

Good luck and let us know how it works out.

Re: Hanger bearing with suspension drop
 

I think some 1/2 tons came with telescopic rear shafts. One guy said you should be good, with a sliding rear, i said no the rear shaft is fixed.

Richard is correct if you have a pillow block, or billet style bearing. The clam shell style does allow for forward to aft movement. I haven't got the new hanger bearing yet (should be here by Thurs) i ordered from Classic Industries...not a lot of info in regards to where it is made, hopefully it has similar flex as OEM.

The plan is to reassemble the driveshaft with all my new u-joints and hanger bearing, and tighten up at just the rear end (at ride height) and see where the bearing sits on the mounting bracket. There is oblong slots to adjust, however i assume i will be outside that range. Once i know where it wants to sit in its natural state, i can determine how far forward i want to move the mounting bracket. Step 2 is install just the slip yoke in the transmission and see how far in it goes. Take off say 1/2" for good measure, and this would be max yoke engagement. Re-install complete assembly and then see how much yoke protrudes out.

HO455 i like your idea about doing a range test. I am about 2" from the bump stops right now. I'm thinking that would translate to about 1/4" of forward movement.

Re: Hanger bearing with suspension drop
 

Ok, hanger bearing arrived, surprisingly at ride height it was within the range of the oblong slots, so moving the bracket forward is unnecessary. On the bench i was able to flex the new bearing approx 5/16" in each direction. Forcing it past this, resulted in the rubber section "popping out" of the clam shell. I did do a suspension range test, however measuring the yoke engagement at the transmission is inconclusive, due to the fact that as the suspension moves up and down, in a static state, the middle u joint is "hinging" and not accurately pushing the driveshaft forward as would happen in a dynamic condition.

I'm not concerned with bottoming out the driveshaft into the trans, as i have over 1 1/4" of yoke protruding at max suspension compression, if the yoke protrusion was less that 1/2" you wouldn't be able to remove the driveshaft.

That being said, i tried taking some measurements from the frame to the rear axle through the suspension travel to measure how much forward movement i was getting, and i didn't see anything significant. Maybe 1/4" total. At ride height i got 2" till bottoming out, and 4" of pre-load, for a total of 6" total travel.

The only concern i have is those two horned flanges that is sandwiched between the bearing (see first pic in post #1) don't fit inside the new carrier assembly. The bottom of the flange won't make contact with the bearing surface. (I hammered out the distortion in the left flange). The size of the clam shell opening seems to be tighter. So what happened is placing both on as factory had it, i was about 3/4" short of the yoke sliding on the splines (sorry i didn't take a photo). Does anybody know what the function of these are? At first i thought maybe a dust/dirt shield, but now I'm thinking maybe it's like a shoe horn, keeps the rubber from separating off the housing. I hope leaving them off isn't going to cause any issues. I think with my truck being lowered 4" in the back help with this as the suspension doesn't travel as much as stock. The other solution would be reshape both with a sharper bell curve. Anybody know if aftermarket ones are available?

Thanks!

Re: Hanger bearing with suspension drop
 

Never seen a two piece shaft design like this before. Learned something, always a good thing. In truth the dimension from pinion to transmission does not change much in almost all suspensions. 1/4"-1/2" is typical. My rear suspension is leaf spring. My custom leaf packs allow about 15" of vertical travel. There is just over 5/8" movement on the slip yoke of the one piece rear shaft from full bump to full droop.