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Mercedes E500 4matic 2006

Hi,
This is the first time it happen to me.
I was dropping off my friend, stopped about 10 feet behind the car in his driveway. my car running and was still in Drive Shift. I got out of the car to help him, forgot to place car in Park Shift. Car started moving slowly.Standby 2-3 persons started pushing car from the front to stop it. in panic, friend turned off the ignition key from the passanger side. Now car started moving Backwards
and rolled down to the other side of the road, till it
stopped by the curb, about 40-50 feet. While it was rolling back there was some grinding noise.
My question is did I damage any thing?
Do I have to worry about any thing?
At present car drives fine. I always drive in “C” mode.

Thanks

Read more: http://mbworld.org/forums/general-mercedes-discussion/474368-problem-my-e500-4matic-2006-a.html#ixzz2FFCjNgj0

Not sure what “C” mode is. All I can say is if it drives and shifts normally with no unusual noises, you probably did no damage. Not sure what the ‘grinding’ noise was, but running backwards with it in gear at a fairly slow speed shouldn’t normally hurt anything. Once the engine was off, the powertrain was effectively disconnected from the motor.

I don’t have enough information on the functioning of the “4-matic” system to say you didn’t harm it; perhaps it isn’t meant to tolerate this behavior. But the damage is either done or not. I’d just drive it and not worry about it unless you notice something unusual happening.

How hard did it hit the curb? There could be tire, wheel, or suspension damage from that.

The grinding noise might be just that the gears are well worn after 10’s of thousands of miles going forward, so the gear geometry is worn in such a way as to only mesh perfectly in forward direction. Backwards, they don’t mesh as well, as they hardly ever go in that direction, so a little gear noise was heard with the car in forward gear, but going backward. This same thing happens to bicyclists. The bicycle chain wears out, so they install a new one, and then the gear noise is very noticeable, often in addition to meshing noise, there is slipping of the sprocket too, which makes a very loud snapping noise. This is all caused because the old chain and the sprockets had worn together, so they meshed perfectly. The new chain isn’t quite the same pitch as the old because it hasn’t stretched, so the new chain/old sproket combo makes noise.

I think unless you observe grinding noises in normal operation, it’s not something to worry about.