The subject is a 92' 300TE 4matic with 109kmi. The symptom is a shudder from the rear coming off a stop that varies in intensity with steering angle (anything +/- 5 degrees of a straight steering wheel). With wheels cut to pin, it'll shake your fillings out. The symptom is present at low speed (15mph or less) in 4M function or test mode, but actually worse in test mode. Dealer replaced the TC under warranty a few months ago anyway, with no effect. (I'm fairly sure 4M is disengaging in test mode - dash warning light is on and the TC clutch thump when coming off a dead stop is absent.) The /!\ active light in the speedo does not come on during the shudder, but does during ignition, so I know the bulb is good.

The only constant seems to be steering angle. The shudder does not occur at any time with steering straight. Any comments would be greatly appreciated.

TIA
Jeff Coco

Sounds like the differential(diff) is locking up all of the time. The diff should lock up only when the 4-matic computer thinks that there is SEVERE slippage. The diff has ""limited-slip"" style clutches that are applied with hydralic pressure. This shouldn't happen durning normal driving!

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Thanks for the reply Doc - the problem is that the shudder is occurring, and is actually worse, with the 4matic system shut off in test mode. My understanding is that the hydraulic unit is shut down in this mode, as you also lose the self leveling rear suspension. Otherwise I agree with you.

I've heard that MB made changes to the 4matic system every year between 91' to 93'. Any chance that the ASD system was made to operate independently from the 4matic? I keep coming back to the other constant which is the steering angle. It would all makes sense if one of the front sensors was sending a bad signal to the hydraulic unit, and engaging the diff lock. I was thinking about disconnecting the ASD control unit as a test, but Alldata doesn't have a good pict of the location, and there are several control units in that area.Any ideas?

Thanks again,
Jeff Coco