worn and broken 12 bolt

[tarafied1]

I bought this 72 Cheyenne a few years ago. It had been sitting in a field. Since I have been driving it and repairing it, the rear end has been pretty noisy. I recently put new u-joints and carrier bearing in it because those were shot and making noise. The rear was still howling under load and clunking on deceleration. I assumed it might be pinion bearings but the yoke "felt" tight.
Well, it finally gave up the ghost! It broke with a loud clunk and hopped up in the air and skidded to a stop. A friend towed me home with his Dodge. The rear was making some pretty nasty sounds as we drug it home.
Pulled the rear cover today and several parts fell out. I fished them out of the pan of gear oil. It appears the spider gear pin was worn so badly it finally broke into multiple pieces. The carrier housing holes are pretty chewed up and one of the spider gears was jammed into the ring and pinion gears. I think the whole differential is toast....

[Willys47]

sounds like if you had just pulled the cover off the diff to inspect, it could of saved some cash and down time. thanks for reminding us not to be complacent when we hear things from our rides.

[Shaky]

It pays to check the U-bolts that hold the rear to the control arms. They tend to corrode down in the control arm and they can cause a clunk. My buddy had a '69 with a clunk that we could not diagnose and the U-bolt finally let go while he was driving it. Great fun...

It sounds like you either need to find a used rear or completely rebuild this one. $$$

[tarafied1]

Originally Posted by Willys47

sounds like if you had just pulled the cover off the diff to inspect, it could of saved some cash and down time. thanks for reminding us not to be complacent when we hear things from our rides.

you are right! I checked the fluid level and it was low. I filled it up and just assumed the noise was the obvious u-joints and carrier bearings. After changing the u-joints and carrier bearing it was quieter but still clunked as you slowed down. Under load it was quiet until you got up to highway speed, then it kind of howled.
Definitely recommend pulling the cover for inspection. It was pretty worn and probably couldn't have been saved(rebuilt) but I would have known how bad it was and maybe could have just replaced the carrier and spider gears.

[leftybass209]

At least you're safe and the break didn't cause an accident. The rear end can be replaced.

[tarafied1]

Originally Posted by leftybass209

At least you're safe and the break didn't cause an accident. The rear end can be replaced.

yes, it could have caused an accident if it had broken at higher speeds. It broke in town but still locked up the rear wheels briefly.
I have swapped out the rear end now. New brake shoes and wheel cylinders too.