Noise from drivetrain

[MBMW]

I posted this question in the M6 forum, but not getting any answers. I figured I post here as well since the M5 and M6 are the same.

I'm getting a thud (bang) when on I'm off and on the accelerator. It happen in sport mode but not all the time. is this part of the cars charm (normal)?

It's M6 MY17 with 29K km on it so far, car is stock. Had the diff main seal replaced due to a leak when I first got it. The work was done at a BMW dealer.

Is this normal or I should take it back to dealer?

[M5Rick]

Take back to dealer, and have the diff holder checked for cracking.

[Boosted M5]

Yep, sounds like diff bushings are done or almost done. Mine is starting to do it and I’m at 66k.

[MBMW]

I appreciate the replies and advice. I did a full pre purchase inspection, diff bushes are good nothing wrong with the vehicle except the diff leak which was repaired by a BMW dealer. Since then I only drove the car 500km. I doubt the diff carrier or bushes are cracked.

will take it back for inspection and report back.

[M5Rick]

Best put it on a rolling road and test it there.

[MBMW]

Originally Posted by M5Rick

Best put it on a rolling road and test it there.

Do you mean curved road?

[MBMW]

The car is at the dealer, checked backlash, removed proper shaft, checked transmission, bushes, suspension, everything within spec and guess what noise is still there.

[M5Rick]

Originally Posted by MBMW

Do you mean curved road?

No, rollers in garage testing for hp and brake testing.

[Singh_96]

most of these cars do it, i've been in 3 and they all had the slight thud, mostly only noticeable in sport plus and 3rd gear lower speeds getting on and off

[MBMW]

Dealer opened a case with Germany, they received instruction to check certain parts and run test, which they've done. Same noise before and after.

Luckily, another M6 came for service, it has the same noise and driving behavior.

Conclusion: normal car characteristics

[KurtsM5]

Originally Posted by M5Rick

No, rollers in garage testing for hp and brake testing.

Dyno?

[Kryp2o]

Originally Posted by MBMW

I posted this question in the M6 forum, but not getting any answers. I figured I post here as well since the M5 and M6 are the same.

I'm getting a thud (bang) when on I'm off and on the accelerator. It happen in sport mode but not all the time. is this part of the cars charm (normal)?

It's M6 MY17 with 29K km on it so far, car is stock. Had the diff main seal replaced due to a leak when I first got it. The work was done at a BMW dealer.

Is this normal or I should take it back to dealer?

What speed do you hear it at? On my F10 i would sometimes hear a thud at the rear when at low speed (less than 50kph). BMW by me said it's considered normal. These cars don't like low speed. My friend with a F80 M3 said he hears the same thing at low speed on his car

[Spacecpe]

There’s a cross brace in the back that’s bolted to the chassis near the rear jack points. Check that. My M6 had a knock every time I reversed or moved forward in 1st and those bolts were a bit loose.

[MBMW]

Originally Posted by Kryp2o

What speed do you hear it at? On my F10 i would sometimes hear a thud at the rear when at low speed (less than 50kph). BMW by me said it's considered normal. These cars don't like low speed. My friend with a F80 M3 said he hears the same thing at low speed on his car

Yes that sounds about right it only happens when lift my from accelerator and back on again at low speeds. I went for an aggressive drive the other day with speeds exceeding 120 kph and tried it, no thud.

Overall I'm not impressed with the Diff, it's an over engineered gimmick. They should've gone with full mechanical LSD.

[MBMW]

Originally Posted by Spacecpe

There’s a cross brace in the back that’s bolted to the chassis near the rear jack points. Check that. My M6 had a knock every time I reversed or moved forward in 1st and those bolts were a bit loose.

Thanks for the tip, I'll check that next time I put the car on the lift.