Loud clunk from rear when going from reverse to drive?
 

I have a '97 E420 with just over 100K mile. Mostly interstate miles driven on good roads. All services have taken care of.

The car has been making a loud clunk when shifting from reverse to drive. The noise comes from the rear of the car. Is this a problem with the driveshaft or differential? What are the possibilities? Thanks

Ever checked the driveshaft front flex disk? It would be the first suspect on my list.

If it's never been replaced I would willingly bet that it needs to be replaced.

Duke

Rear differential bushings?

My '86 300E had that *clunk* sound and feeling when going from 'R' to 'D' until i had all the bushings replaced. -My rear diff. bushings were totally shot.
Don't know if this applies to the '97 E420 though..

Freestyler

I am not familiar with your car but sure sounds like diff bush. Easy to check. If the propeller shaft moves when you push on it then find out where it is loose. It should be nice and tight when good.

On the w124 the bushings are stressed by the rotating motion when the driveshaft is engaging either way.

My bushings looked like this:

OK. Looks like I need to take a look at this bushing. Where is it (are they) located?. Are they located where the differential mounts to the car frame or are they actually at the point where the driveshaft enters the diffy? Thanks again.

They are located where the diff meets the frame -on the back of the diff.

Freeestyler

Thanks!

There also may be one up front by the tranny-or whatever duke2.6 said.

The flex disk I was referring to is between the transmission and driveshaft. They are typically cracked by 60K miles and the driveline develops slop. The rear flex disk is more longer lived.

Duke

So flex disc = bushing? Or is it some kind of other animal?

What is the procedure to change the differential bushings? Can it be done in car or does the whole diff carrier have to be removed?

Haasman

The flex disk I referred to is at the front of the driveshaft, which is quite different and physically removed from the axle mount bushings.

Duke

Let me rephrase my question: Can the axle mount bushings be replaced while the carrier stays in the car?

Haasman

The differential bushings are a likely prospect, but so is the flex disc (front). I also wouldn't rule out a cracked motor mount.

To test for a bad motor mount, you can put the car in reverse, and with your foot firmly on the brake pedal, gently rev the engine and have someone look at your engine. If it jumps up slightly, then it's your motor mount.

Repeat the procedure by putting the car in Drive. If it jumps, then it's the other motor mount.

Thanks for all the info. It seems like the noise is actually coming from the rear axle/diffy area, so unless the REAR flex disc is bad, I don't think it is the front flex disc. I'll check the motor mounts next.