"Low/Medium Load" driveline pulsating noise/knocking

[v8z4]

I'm getting a pulsating vibration sound out of the right rear above 60MPH. It only occurs under low/medium load conditions (maintaining-to-slight acceleration condition).

At WOT, the knock goes away till around 95mph but even then it is very minor.

If I let off (no load), the knock goes away entirely.

Changing gears does NOT affect the knock (3rd/4th/5th = same noise level).

Again, it is ONLY on the right rear. It is not a "slap clunk" that occurs on rapid application/removal of power (such as bad driveshaft/worn gears/etc.).

The car has band new (less than 1K miles) aluminum cradle mounts and spherical suspension, so I know it's not worn out suspension. There is NO rattle/clunk out of the suspension over rough road (unless at low/medium load).

I found this:

SYMPTOMS OF CV JOINT FAILURE
Bad boots are not the only thing you need to look for. You also need to listen for noise or complaints that might indicate a CV joint problem. These include:

*
Popping or clicking noises when turning. This almost always indicates a worn or damaged outer CV joint. To verify this condition, place the vehicle in reverse, crank the steering wheel to one side and drive the vehicle backwards in a circle (check the rearview mirror first!). If the noise gets louder, it confirms the diagnosis and the need for a new CV joint or replacement shaft assembly.

*
A "clunk" when accelerating, decelerating or when putting the transaxle into drive. The noise comes from excessive play in the inner joint on FWD applications, either inner or outer joints in a RWD independent suspension, or from the driveshaft CV joints or U-joint in a RWD or AWD powertrain. The same kind of noise can also be produced by excessive backlash in differential gears. To verify the condition, back the vehicle up, alternately accelerating and decelerating while in reverse. If the clunk or shudder is more pronounced, it confirms a bad inner joint.

*
A humming or growling noise. Sometimes due to inadequate lubrication in either the inner or outer CV joint, this symptom is more often due to worn or damaged wheel bearings, a bad intermediate shaft bearing on equal length halfshaft transaxles, or due to worn shaft bearings within the transaxle.

*
A shudder or vibration when accelerating. May be caused by play in the inboard or outboard joints, but the most likely cause is a worn inboard plunge joint. Similar vibrations can also be caused by a bad intermediate shaft bearing on transaxles with equal length halfshafts, or by bad motor mounts on FWD vehicles with transverse-mounted engines.

*
A vibration that increases with speed. This symptom is rarely caused by a failing CV joint. An out-of-balance tire or wheel, an out-of-round tire or wheel, or a bent rim are the more likely causes.

Anyone had experience with this sort of issue?

On the e46 board, individuals talked about re-greasing the CV joint to help:
http://forum.e46fanatics.com/showthread.php?t=631252
anyone done this?

Thanks,
Chris

 

[v8z4]

After taking nearly everything in the rearend apart, it turned out to be one of the brand new 80,000lb rated spherical bearings. It had lateral play between the ball and race, allowing the trailing arm to slop. It went bad immediately (as in first time I drove the car after installing the spherical bearings) so it must have been a faulty unit. I swapped in a new bearing and everything is quiet as can be.