I have a '68 122 that I want to sell. I recently listed it on e-bay and the item sold. The high bidder came to get the car and took it on a test drive. He came back saying he thought the rear end is bad and that he could not complete the sale. I don't want to force anyone to buy the car who doesn't want to, but now I am concerned about the rear end issue. I took the car for a drive and there is a noise coming from underneath. It happens under power when going straight or turning. It is a pulsating noise that increases with speed. How can I determine if the problem is a bad rear end? If the rear end is no good what is the best (most economical) way of fixing it. I have extended an offer to the next-highest bidder to buy the car, but don't want to misrepresent its condition.

In addition to what George said, check the rubber "donut" that holds the center driveline bearing. You should not be able to deflect it more than 1/4" by hand, if even that much.

I'd check the U-joints and center bearing, also tranny mount and maybe
the rear suspension bushings. There has also been a rash of loose
companion flanges lately on this board, which would also do that.

Make sure the diff has lube in it and that it is not full of sparklies.
What you describe, however, does not sound like a differential problem.

Couple other things to check would be lug bolts and axle nuts.
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George Downs, The "original" Walrus3, Bartlesville, Oklahoma

George:

Thanks for your note. The flange bolts are all tight, as are the lugs and axle bolts. The center bearing is fairly new and seems to be OK, and the U-joints seem to be fine as well. I wonder if the drive shaft is out of balance or bent? Any experience with what that sounds like? There is some play in the rear end. If I grab the drive shaft I can rotate it a bit before it stops.