Wheelbearing/driveshaft/ gearbox noise
 

I hope someone can help me - I am running out of ideas for possible solutions.
I own a 92 440 with a M55-373M gearbox- milage 440.000 km. I love the car and it has been running smoothly until a noise from the front left corner called for a remedy. The noise appears when the steering wheel is turned slightly to the right. I figured it was a wheel bearing so I exchanged it for a new "QH powerdrive" unit. It did not cure the problem. I tried running in circles at low speed to listen for possible "clonk" noises from a worn CVJ - but none appeared. I tried exchanging the wheel - no change.
I tried running on the special sparewheel with a smaller diameter to see if the rotation in the diff occuring when turning was making the noise - but no sound heard. As the sound was getting worse I located a spare car for wrecking and test drove it thoroughly while listening for "Sounds" - but it was quit - I the exchanged gearbos, driveshaft and the entire strut including wheel carrier, bearing and braking disc - and OOPS now the sound was STILL present in my car!!
I am afraid that I might actually be reproducing the error when I exchanged the parts - are there any ways I can be "Creating" the noise by incorect assembly? I have tried to be observant on the correct tightening torque for the center nut on the drive shaft - is it possible that the bearing is destroyed by only very smal deviations from correct torque?
I must say that I have lost track of the "original" position of the tripod (or spider) but can it really be making that much noise, and why only when turning to the right and nothing when turning to the left?
I have checke the springs and motor suspension rubbers they are OK.

A failed wheel bearing will make a louder noise when turning to one side, and less noise when turning the other way. The noise will increase with side load transfer during cornering. If the noise you hear occurs only when turning slightly, and not on full lock, it is probably something else, as you already know from all your parts swaps. If we assume it is none of those swapped parts, then the problem must lie in something that remained in the car after the swaps. One possible culprit is the sub-chassis, the frame that holds the suspension together. It can be cracked, it can be loose on one of the mounts, there can be a broken bolt, or even the chassis rails where it attaches can be cracked from corrosion. I would try the following: put the front of the car on stands, located under the main chassis rails, not on the subframe. Do this with the steering in the same position that produces the noise. Then after making sure the car is REALLY secure, push and tug at the wheel, strut and triangle and see if you can see any slack on undue movement. Compare the reactions on the left side with the reactions on the right side. I`m willing to bet ther is something broken/bent/cracked somewhere, and the freedom motion felt on the right is greater than on the left.

I forgot one obvious possible cause - the power steering. Sometimes the rack can get worn out at around the center position, from spending much time in that position, and one of the possible symptoms is noise. I`d check it out.

DF