Mysterious "bang" when backing up... - PeachParts Mercedes-Benz Forum

acmathis · #1 06-23-2006, 05:57 PM

Okay, I'm not sure what to make of this one. My girlfriend puts the 1999 ML430 in reverse today, and proceeds to back up. The following are excerpts from the chat conversation.

Her: "btw my car did something weird today."

Her: "I got in it to go the hair place, put it in reverse and as I started to back up it made a huge bang and sorta felt like I had backed into something"

Her: "I was like did a car pull up in the driveway and I didn't see it"

Her: "and then it was fine... but its driving kinda shaky - like the steering is loose or something"

Her: "reminded me of when the axle broke on my dads car when I was young"

Me: "hmmm...odd...is anything leaking out of the bottom?

Her: "nope"

Me: "and you can't really feel where the vibration is coming from?"

Her: "like I said the steering feels a little loose and the back end seems to be loose as well kinda feels like a wheel is going to fall off...can't really describe it"

Her: "I thought hmm did some stupid kid come loosen the bolts on a wheel?"

Me: "where the the "bang" sound come from, or did you even notice?"

Her: "the bang was definately from the back... like the brakes locked on the wheels or felt like I backed into something"

I am, of course, working in Seattle, and the car is in Montreal, so I won't be able to physically look at it until sometime next Tuesday.

Any helpful suggestions from anyone? Transfer case, u-joints, rear pinion bearings, rear wheel bearings, parking brakes, rear brakes, rear CV joints, or any suspension components that might bind and break? Don't suggest the driveshaft center support bearing, because there isn't one. It's a Canadian-spec vehicle, and has a one-piece rear driveshaft.

The only wrenching I have done on the back end is replace the rear shocks with factory units last year, and replaced the fuel filter and lines with the new style last week. On the front, I've replaced the left upper control arm and the front shocks. It has had an overall vibration in the vehicle at 120-140 kph that I have been unable to figure out to this date.

Hopefully it is nothing major, but loud "banging" sounds generally are expensive. Thanks in advance for your assistance.

mbdoc · #2 06-26-2006, 08:25 AM

Very little chance to find that problem unless it happens again...HAVE seen several transmissions do that & also the transfer case... Possibly codes will show up in 1 of those 2 computers...