Weird Clunk/Thud in rear

[NY-F10]

Hey guys. I have a 2014 BWM M5 that I daily. Finally hit 88,000 miles and car has been amazing. Before I say anything I wanna state this.

Yes - I have a solid diff mount, it's made by German Autowerks with the delrin bushing.

Anyways, today I did a pull from a stop light and hooked pretty good and then heard a clunk and let off my gas. I pulled into the parking lot of the bank I was going to and turned off my car and looked under to see if any obvious damage. There wasn't. Anyways went in did my business and came back out and started my car and it drove perfectly fine after. Didn't romp it all just drove normal. Then I tapped the brakes to go on a highway entrance ramp and heard the clunk while turning. Drove rest of the way normal. Came to my exit and came to the red light. All was fine and tapped the gas again when it turned green, keep in mind I'm being soft now and not romping because I'm worried.. and I hear clunk. Drives normal and shifts normally. Come to my neighborhood and hear the clunk when I brake again- so no throttle at all. Then preceded through the stop sign and into my driveway with no issues. Any help here? Could it be mounts?

I checked the skid plate in the rear by the exhaust and all bolts are tight. Felt my axles from under the car (should do this on a lift) and there was no play at all. Im stumped. I have a friend with the same issue for the last 15k miles for him and he told me to ignore it and said probably was the transmission mounts. I just wanna make sure I don't destroy anything and wanna catch it before something expensive happens.

Should also mention. I am on stage 1 dinatronics which gives indicator to power level and possible wear on car from tune.

[fstm5]

Originally Posted by NY-F10

Hey guys. I have a 2014 BWM M5 that I daily. Finally hit 88,000 miles and car has been amazing. Before I say anything I wanna state this.

Yes - I have a solid diff mount, it's made by German Autowerks with the delrin bushing.

Anyways, today I did a pull from a stop light and hooked pretty good and then heard a clunk and let off my gas. I pulled into the parking lot of the bank I was going to and turned off my car and looked under to see if any obvious damage. There wasn't. Anyways went in did my business and came back out and started my car and it drove perfectly fine after. Didn't romp it all just drove normal. Then I tapped the brakes to go on a highway entrance ramp and heard the clunk while turning. Drove rest of the way normal. Came to my exit and came to the red light. All was fine and tapped the gas again when it turned green, keep in mind I'm being soft now and not romping because I'm worried.. and I hear clunk. Drives normal and shifts normally. Come to my neighborhood and hear the clunk when I brake again- so no throttle at all. Then preceded through the stop sign and into my driveway with no issues. Any help here? Could it be mounts?

I checked the skid plate in the rear by the exhaust and all bolts are tight. Felt my axles from under the car (should do this on a lift) and there was no play at all. Im stumped. I have a friend with the same issue for the last 15k miles for him and he told me to ignore it and said probably was the transmission mounts. I just wanna make sure I don't destroy anything and wanna catch it before something expensive happens.

Should also mention. I am on stage 1 dinatronics which gives indicator to power level and possible wear on car from tune.

Sounds like your diff, especially if it clunked while you're turning

Or possibly your axles?

[M5_Raz]

Sounds like something came loose in the rear end. Without being able to hear it and see it, there's not much we can help with.

I'd take it in because it's not a normal sound. Just because your friend lives with it doesn't mean it's good/normal imo.

[NY-F10]

Originally Posted by M5_Raz

Sounds like something came loose in the rear end. Without being able to hear it and see it, there's not much we can help with.

I'd take it in because it's not a normal sound. Just because your friend lives with it doesn't mean it's good/normal imo.

Yeah I'm going today. Have a friend who is a tech at BMW. It only happens under 1300 RPM I've figured. The lower the RPM the worse when I tap the throttle. Honestly might be a bushing or mount or something

[NY-F10]

Snapped bolts guys. Thank god one held on

[M5_Raz]

Wow! Good thing you checked, that's on the axle?

[NY-F10]

Originally Posted by M5_Raz

Wow! Good thing you checked, that's on the axle?

No it's my upgraded diff bracket. The bolts for it snapped. Must've been some sort of error in installation. I did a really hard pull too

[fstm5]

That could have ended bad so quickly lol Good thing you caught it fast

[1320racer]

Originally Posted by NY-F10

No it's my upgraded diff bracket. The bolts for it snapped. Must've been some sort of error in installation. I did a really hard pull too

Hmmm. Still not clear. Please show a clear pic where the sheared off bolts pass through.

[1320racer]

Originally Posted by 1320racer

Hmmm. Still not clear. Please show a clear pic where the sheared off bolts pass through.

Is it the bottom left side of the diff mount/support? Pic is kind of dark.

[NY-F10]

Originally Posted by 1320racer

Is it the bottom left side of the diff mount/support? Pic is kind of dark.

It was bottom left and top of diff bracket bolt locations. I still haven't gotten to fixing it. Currently sitting. When I get it back on a lift I'll post more detailed pics. Have to extract the bolts stuck inside the diff- aka I have to drop the diff completely

[m5dream]

jeeez those are like 12.9 grade hardware and they snapped thats worrying