Drivetrain clunk when releasing and pressing down on gas pedal - Mercedes-Benz Forum
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post #1 of 50 (permalink) Old 05-26-2019, 04:46 PM Thread Starter
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Drivetrain clunk when releasing and pressing down on gas pedal

Concerning my 1992 500SL. I've been having a clunking noise when I press down on the gas pedal and releasing the gas pedal. Its getting worse and louder. When the car is on the lift, wheels hanging, car in Neutral and if I rotate the driveshaft I hear that clunking noise and feel play in the shaft (feels like a half + an inch of play). I can shake the shaft and see (I removed all the shields) that the u-joint and bearing are solid with NO play and I cannot hear a noise. ONLY when I rotate the shaft back and forth I can hear the noise and feel the play. It appears like I have play in the rear differential but I hear louder and feel more play coming from the rear of the transmission. My MB flex disc are 6 months old and show no cracks. Motor mounts, strut mounts, transmission mount, all have been recently replaced. Anyone have an opinion or any thoughts for further checking. Just hope it's not the transmission. The transmission shifts perfectly smooth. BTW, I have search the forum with no results.
Thanks,
carltwo
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post #2 of 50 (permalink) Old 05-26-2019, 06:08 PM
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Dumb question, but did you check your lugnuts/bolts?
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post #3 of 50 (permalink) Old 05-26-2019, 06:44 PM Thread Starter
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Dumb question, but did you check your lugnuts/bolts?
Yes, 80 foot pounds
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post #4 of 50 (permalink) Old 05-27-2019, 06:21 AM
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Originally Posted by carltwo View Post
Yes, 80 foot pounds
Check rear control arm bushings. All rear bushings for that matter.

John;
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post #5 of 50 (permalink) Old 05-27-2019, 07:10 AM
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Check rear control arm bushings. All rear bushings for that matter.
This. At one point, I had a loose bolt in the rear multi-link. I mostly felt it on deceleration - where the rear would wiggle a little. When accelerating, I'd hear a clunk. It was one of the control arms rotating up and hitting the connection point. Reinstalled the new bolt and hardware at torque spec. No more noise, and no squirrely rear.
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post #6 of 50 (permalink) Old 05-27-2019, 12:47 PM
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Disconnect the driveshaft from the diff.

With the driveshaft loose from the diff, rotate the diff input back and forth while listening for the clunk.

With the driveshaft loose from the diff, rotate the "still connected to the tranny" driveshaft (in neutral) while listening for the clunk.

Which one clunks?

Each end of the driveshaft also has a center bearing, I wonder if your's were damaged during your disc refresh.
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post #7 of 50 (permalink) Old 05-28-2019, 10:21 AM Thread Starter
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Originally Posted by mahunt View Post
Disconnect the driveshaft from the diff.

With the driveshaft loose from the diff, rotate the diff input back and forth while listening for the clunk.

With the driveshaft loose from the diff, rotate the "still connected to the tranny" driveshaft (in neutral) while listening for the clunk.

Which one clunks?

Each end of the driveshaft also has a center bearing, I wonder if your's were damaged during your disc refresh.
Thank you everyone. All the rear bushings appear to be fine. Tomorrow I will check loose bolts and if everything is tight then will continue and remove the driveshaft from the differential as to what "mahunt" has suggested and report back.

Last edited by carltwo; 05-28-2019 at 10:26 AM.
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post #8 of 50 (permalink) Old 05-28-2019, 01:33 PM
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Double-check your Engine and Transmission Mounts.

I realize that they were replaced recently, but new parts can fail..


-
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post #9 of 50 (permalink) Old 05-28-2019, 03:25 PM Thread Starter
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Originally Posted by guzzimike View Post
Double-check your Engine and Transmission Mounts.

I realize that they were replaced recently, but new parts can fail..


-
Mounts are all good, they were purchased from the dealership last year.
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post #10 of 50 (permalink) Old 05-29-2019, 02:18 PM Thread Starter
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Hi all,
Today I completely removed the driveshaft. I'm trying with no success to attached 2 videos. one to hear the play from the transmission and the other to hear the play in the differential, this is after I removed the driveshaft, Can anyone explain how to upload a video ?.
I have a friend who has a 1991 500SL and I checked his driveshaft and there's definitely not as much play on both ends of his driveshaft as I have. I also checked out the u-joint and center bearing while the driveshaft was removed from the car and all is just fine. I also attached a photo as I did fine a crack in a rubber seal at the end where the driveshaft attaches to the differential, not sure if this means anything. Please, your thoughts...
Thank you
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