1968 Dart sudden rear end noise.

George Jets said

First off a 7 1/4" rear end is a very light duty rear end.

As the small 2 spider gears start to wear, it wrenches on the cross pin in the case. So much so that it eggs out the case that the cross pin sits in.
Eventually it sheers the the 3/16" bolt pin on the end and the cross pin starts to work out.

They used to sell diff rebuild kits on rock auto for the later year a bodies. New pin, spider gears, side gears, shim washers and anchor pin/bolt.

In reality not much fixing them when the diff case wears out from the cross pin moving.

Last ditch hillbilly effort > weld the cross pin into the case and start looking for an 8 3/4 as a replacement.

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Wow. I didn't think these rear ends were absolute trash that coukdnt be rebuilt when they fail. Most things from the 50's and 60's can always be rebuilt. Chrysler put tons of them in these in A bodies and I've seen people state they lasted a couple hundred thousand miles. If they were such junk why did Chrysler put these behind 273's and 318's knowing they wouldn't hold up? Youd think their pride and reputation for being "the engineering company" would be on the line. B bodies never used this rear end I take it. My next question is if it's all doom and gloom and the rear end can't be properly rebuilt to last,how hard to find is an 8 3/4" rear end that will drop on with no modification?.