Technical Bent 12 bolt rear end?

What’s your guys thoughts on this? I picked up this 49 gmc pickup project half done that already had this 69 Camaro 12 bolt rear end. Yesterday on a drive I made it about 45 miles till I pulled over and heard some clunking from the rear. Sounded like I was about to lose my pass side wheel. I pulled the wheel off and had some grease in the drum so it seems I blew the bearing but it didn’t seem to have a bunch of play. I had noticed the passenger side seems to be bent on the same side I had the bearing issue?The truck drove okay so I’m assuming it’s the rear end housing is bent and not the axle? Whats your thoughts from the picture? Thanks

 

How about a shot of the whole rear end with different view's.

 

Could be bent backing plate?

 

Certainly looks like it.

 

Does seem to be the backing plate now that I look at it. I’ve never noticed any excessive drag but I’m assuming that could cause the bearing to burn up also? Whats the best way to fix a bent backing plate? Bend it or just replace you guys think? I’m assuming I should probably double check the axle at the same time

 

Bend it back.

 

Replace the backing plate.

 

Any ideas on how to bend it back? Maybe talk to a collision shop?

 

Just get another backing plate, it will be hard to bend it back to the correct position. While the wheel is off and the car jacked up run the car in gear and watch the flange that the drum mounts on, to see if it's bent. Should be obvious if it is as it will wobble. Do this with caution and be careful as usual so the car doesn't fall off the stands.

 

I believe 10 and 12 bolt Chevy backing plates are the same..

 

I would pull the axle and backing plate and check the axle flange for straightness if it were me.

 

Don't be in a hurry to dismiss the possibility of a bent tube. In a prior career, I was a maintenance crew lead for an amphibious sightseeing operation, and we used tandem 2-1/2-ton GMC axles in the rear of the vehicles. We kept breaking driver-side axles on one of them, and it wasn't until, like, the 5th one that I decided to pull the passenger side axle and look through one tube end to the other. Sure enough, driver's side was bent towards the rear near the pumpkin. It can happen.

 

Put a dial indicator on there barely touching the axle shaft . Turn the axle and see if it has any blips in the readings...... Replace bad backing plates Here is a U Tube video on axle run out, and what to look for. Cheap insurance.



https://www.google.com/search?q=che...57j33i160l4.8536j0j7&sourceid=chrome&ie=UTF-8

 

My Dana 60 with 3/8" thick wall tubes was way off and needed to be straightened with a combonation of heat and a giant press

 

J -

If the truck is a "driver"...yeah, check the housing.
Pull the axle out and check the actual housing for being straight. Unless the car / truck has, fallen onto the backing plate, I doubt that thats the problem.
Hard use in a truck is more likely the culprit of a bent axle.
A bent housing will burn up bearings also.

Either replace it, or possibly heat and a press, may straighten it.

Mike

 

There must be something funky with the braking with the shoes so far out of alignment to the axle flange. Brakes must be backed right off to just get the drum on and there'd be minimal contact, so minimal braking, or excess drag / rubbing. This makes me wonder how it could ever have been in use in that condition, if it ever was!

Chris

 

I don't think you could have tube bent enough to cause the backing plate to not align with the drum. You could have a bent flange or more likely a bent backing plate, or even rust on the flange keeping the backing plate from seating properly. Check the four bolts hold the backing plate on. While the tire is off, lift up on the axle and see how much movement it has side to side and up and down. It should be tight in all directions with just a slight in and out movement.

What kind of wear marks are on the brake shoes?

As far as grease seals leaking, 12 bolt axles have a hardened surface the wheel bearing rollers ride on,
( no inner bearing race ), axle wear causes seals to leak. There are kits available that relocate the bearing and seal. 12 bolts use C-clips to hold the axles in, you drain fluid, and pull the center pin to remove axles.
https://pontiworld.com.au/usgmsp/product_info.php/products_id/5284

For a fast and easy test, wrap a piece of stiff wire around a wheel stud and cut to length for a pointer. Bend wire to backing plate and spin the axle looking to see if the axle flange wobbles, or if the backing plate is bent. A dial indicator will do the same if you have one.

 

So I just used a square with a level real quick measuring off the backing plate bolts on the flange and the pass side seemed to be a bit off vs the driver side. Next step is gonna be start pulling a part and dig deeper. Im assuming if the flange is bent I’m looking at replacing the axle? I doubt any shops near me straighten axles these days.

 

looks like a bent backing plate replace it but while it is apart indicate the axle flange

 

Even if the flange is bent, you can still bend the backing plate in the correct location. The flange is 3/8" thick and really tight to the housing, it would be pretty rare for it to be bent without some sort of other noticeable damage.
Just use my wire method, dial indicator, or steel rule and measure from axle flange to backing plate in four spots.
With a couple of large C-clamps and short steel bar across the axle flange, you can pull the backing plate back into position. Just keep checking as you go and be sure the axle flange is straight first.

That is a pretty rare rear axle assembly, so don't be in a hurry to get rid of it.

 

As a double check, put your level on the lip of the brake drum.

 

Don't think a bent backing plate could cause bearing trouble. Has this rear end been narrowed? If it was cut and welded out near the flange a slight misalignment would explain it.

 

Did it have new spring perches welded on? We had one where the heat from welding bowed the tubes.

 

This is a 12 bolt that had a BUNCH of bad welding on it, it was in use, I'm sure trashing bearings, and wearing out the spline in the posi side gears?!?! Takes a lot less heat and welding to bend a tube than people think!!! That is a 1 1/2" dia. line up bar for narrowing rear ends

 

How do you know your housing is level to the world ?

 

Bad bearing surface, https://www.agcoauto.com/content/news/p2_articleid/137
You will know when this happens, gear oil goes everywhere!

 

Where is near you?

 

Dirt track racers know where to get a housing straightened.

Gary

 

Santa barbara