I posted a few days ago that I have a 122 for sale and the potential purchaser declined the car after driving it, saying he thought the rear end was bad. The car makes a pulsating noise under power--no knocking or thumping, but increases with speed. The flange bolts are tight, center bushing and rubber recently replaced, and I believe all the U-joints are good.

I pulled the housing off the rear end and don't see any bad teeth or chips of steel inside. It does seem to have a fair amount of play, but I don't really know what is normal. Now the questions:

1) Could the pulsating sound be caused by a bent or unbalanced drive shaft?

2) How much play should exist in the rear end?

3) Can I put the rear end from a '73 1800 in its place?

4) If so, do I have to replace the entire rear axle or can I just put the guts in and retain the drum brakes?

Remember I am trying to sell this car. I don't want to invest a huge amount of time or money in it, but I do want it to be solid when I sell it.

Thanks!

Tim

Do the yokes on your front driveshaft line up perfectly? If not they
will cause pulsing because you are not canceling out the changes in
rotational velocity. That is pretty easy to fix, just drop the rear
end of the driveshaft, pull out the spline and re-stab it where they
do line up. The worst case for this is to have them 90° apart.

This doesn't sound like anything in the differential, but if your
driveshaft has a flat spot or obvious bend in it that might also
cause such a thing. A bent wheel or a lump on a tire could do the
same thing.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma

George-
Could you explain this in a bit more detail? My 122 has a very noisy drivetrian as well. Not so much of a pulsating sound, but more of a constant whine that gets louder and higher in frequency with road speed. I'm not sure what the yokes are that you refer to, but I'd like to check mine.

Thanks-
Eric
--
'66 122 Coupe 110k '97 850 Wagon 130k

If you've got a whine it is probably either in the differential or the
tranny - that's where the gears are. Whines come from gears first,
maybe bearings but more likely gears. Check the lube in your differential
and tranny, and note if there are metal flakes. If so that is where your
problem lies.

Yokes: Look at your rear driveshaft and note how it has one yoke at each
end and they are exactly aligned. The front shaft has a slipjoint in it
but also has two yokes, one at each end. They must be aligned the same
way (relative to each other) as the yokes on the rear shaft. If not, you
will get pulsation or thumping because of the uncanceled change in rotational velocity when the u-joints work against each other rather than together.
If they are not aligned correctly you gotta drop the rear shaft, pull
the slip joint apart, turn it until the yokes line up and stab it back
in.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma