For those interested or having idler groan, cross posting this from similar discussion ion BW forums:

After chasing the idler groaning noise, I came to conclusion that if I do this again, I will not put any grease in the chassis tube or on the outside of the rubber sleeves. If they are too tight a fit, maybe a very little dish soap or Pledge or similar on just the edges of the rubber flutes so the sleeve can be pulled in. The rubber should, I believe, be a tight fit.

Where a light coating of oil or grease or dry lube might help, is between the flanged metal sleeve and the thin metal sleeve that is embedded in the rubber sleeve. Perhaps also put some grease in the gap between the rubber inserts in hope some of it may get between these sleeves.

I believe the groaning noise in my case, was the upper rubber sleeve turning in the chassis tube. This should not happen. The flanged metal sleeve should turn in the metal sleeve that is embedded in the rubber.

I believe problem starts in the end caps. The 120 NM torque should compress the assembly without compressing the washers that are on inside face of the flanged sleeve (See post #11 above items 1, 2 & 3). The FSM says, there can be up to 0.5mm slack after torqueing the bolt. If there is no slack, that flanged end cap joint can lock up and force the rubber sleeve to rotate in the chassis tube, causing the groaning. This is what led me to do the measurements and install the shims.

Could be that this is vehicle or vendor specific. I did this on my 72 107 with Lemfoerder kit. Part number is same for many Benzes from 68-95. If there is a next time, I will again measure the chassis tube and the replacement parts for fit! And probably buy the more expensive MB kit.

By the way, the rubber parts of the Lemfoerder kit have the MB part numbers and the Phoenix symbol (Company in Turkey that makes many OE MB rubber parts). The metal parts may be where the discrepancy is. It would be interesting to compare aftermarket dimensions with the MB part.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5