Rear noise when accelerating

[SuperF10]

I have this crunching noise that happens every time the car starts from 0mph. If the car is going above 3mph and I accelerate it usually doesn't make the noise. It sounds like it's coming from the rear suspension. Has anyone had this issue before?

It cropped up for me about 5 months ago and has gotten progressively worse to the point that the rear makes the crunch noise every time I accelerate from 0mph. The rear pads and rotors were replaced about a year ago, so I don't think it's a brake issue.

[M5Rick]

Originally Posted by SuperF10

I have this crunching noise that happens every time the car starts from 0mph. If the car is going above 3mph and I accelerate it usually doesn't make the noise. It sounds like it's coming from the rear suspension. Has anyone had this issue before?

It cropped up for me about 5 months ago and has gotten progressively worse to the point that the rear makes the crunch noise every time I accelerate from 0mph. The rear pads and rotors were replaced about a year ago, so I don't think it's a brake issue.

First thing to do is check the rear diff mount for cracks.

[Dwaynos]

Check the rear brace bolts underneath, they're not properly tight it would cause the noise you are describing.

[SuperF10]

Pretty sure something in the rear end is toast. Last night it was raining and I gave it some power at a stop sign and BOOM something exploded in the rear. Had to push the car pretty far home. I’m going to call the dealer and get it towed today. From poking around it looks like the drive axle is done. My car is bone stock though so I have no idea why it would do that. 2nd time stranded in this car, the first was because of injectors.

[M5Rick]

Originally Posted by SuperF10

Pretty sure something in the rear end is toast. Last night it was raining and I gave it some power at a stop sign and BOOM something exploded in the rear. Had to push the car pretty far home. I’m going to call the dealer and get it towed today. From poking around it looks like the drive axle is done. My car is bone stock though so I have no idea why it would do that. 2nd time stranded in this car, the first was because of injectors.

Give us a pic if you can when it's on ramp.

[SuperF10]

Originally Posted by M5theonlyone

Give us a pic if you can when it's on ramp.

Will do. I’m in shock of how loud the explosion was. I had my little brother in the car with me and he’s like “my heart is beating so fast right now” LOL. From what I read, people say that the CV “grenades”. So I am assuming that’s what happened. It was terrible, you could hear just metal banging and shaking after the explosion.

I’ve got an A/M warranty that’s never denied a claim on two of my BMWs so hopefully it will be quick and painless. I have never done a single mod to the car in fear of warranty denial so I think I’m in the clear. I’ll keep it updated though. Flat bed is on the way to my house.

[M5Rick]

Originally Posted by SuperF10

Will do. I’m in shock of how loud the explosion was. I had my little brother in the car with me and he’s like “my heart is beating so fast right now” LOL. From what I read, people say that the CV “grenades”. So I am assuming that’s what happened. It was terrible, you could hear just metal banging and shaking after the explosion.

I’ve got an A/M warranty that’s never denied a claim on two of my BMWs so hopefully it will be quick and painless. I have never done a single mod to the car in fear of warranty denial so I think I’m in the clear. I’ll keep it updated though. Flat bed is on the way to my house.

Yes so long as it's contained shouldn't be too bad, what you don't want is the diff support breaking then diff and d/shafts being dragged on the road.

[SuperF10]

Originally Posted by M5theonlyone

Yes so long as it's contained shouldn't be too bad, what you don't want is the diff support breaking then diff and d/shafts being dragged on the road.

They said my axle compression bolt snapped and the spindles are destroyed on the axle shaft, the hub and the diff seals.

How the hell does the axle compression bolt snap?

[M5Rick]

Originally Posted by SuperF10

They said my axle compression bolt snapped and the spindles are destroyed on the axle shaft, the hub and the diff seals.

How the hell does the axle compression bolt snap?

Looked up and this bolt with spring has a torque of 210nm,secures axle to wheel hub..says it should be replaced and not re-used when undone with work done in that area.

[Blaxwil]

Originally Posted by M5theonlyone

Looked up and this bolt with spring has a torque of 210nm,secures axle to wheel hub..says it should be replaced and not re-used when undone with work done in that area.

There it is. What kind of work requires you to remove that bolt?

[M5Rick]

Originally Posted by Blaxwil

There it is. What kind of work requires you to remove that bolt?

Anything that requires d/shaft removing for instance replacing damaged uj boots, or shafts themselves,possibly wheel bearings from hubs which need to be pressed out and of course accident damage like striking a kerb hard.

[Dwaynos]

If it is the bolt mentioned above then you will probably find that the spines on the shaft and bearing will both be damaged, especially if the bolt has been loose for a while.

Obviously the rest depends on whether or not the shaft came far enough away from the hub to spin around and damage anything else.

[SuperF10]

Originally Posted by Dwaynos

If it is the bolt mentioned above then you will probably find that the spines on the shaft and bearing will both be damaged, especially if the bolt has been loose for a while.

Obviously the rest depends on whether or not the shaft came far enough away from the hub to spin around and damage anything else.

Yes, the bolt basically unscrewed itself and then the splines got destroyed. No idea why at first the SA was saying that the bolt snapped. It did not snap, the threads are flat halfway up the bolt lol.

I'm replacing the axle shaft and the hub assembly.

[SuperF10]

Originally Posted by M5theonlyone

Anything that requires d/shaft removing for instance replacing damaged uj boots, or shafts themselves,possibly wheel bearings from hubs which need to be pressed out and of course accident damage like striking a kerb hard.

This post is 4 months old, you're right on the money. I replaced my hub and reused the compression bolt like a dummy.

The dealer wanted like $4k+ to do the work. I got a salvage shaft for $275 shipped to my house off a totaled M5 that only had 15k miles, bought a new OE hub for ~$370 and then replaced basically all of the mounting hardware for the rear suspension while I was down there. All in all it was less than $1k. The repairs have held up great, I have put about 5k miles on the car since and no issues.

If anyone reads this... if you ever take that compression bolt off, replace it! Also don't be afraid of recycled parts, they save a ton of money.

[M5Rick]

Originally Posted by SuperF10

This post is 4 months old, you're right on the money. I replaced my hub and reused the compression bolt like a dummy.

The dealer wanted like $4k+ to do the work. I got a salvage shaft for $275 shipped to my house off a totaled M5 that only had 15k miles, bought a new OE hub for ~$370 and then replaced basically all of the mounting hardware for the rear suspension while I was down there. All in all it was less than $1k. The repairs have held up great, I have put about 5k miles on the car since and no issues.

If anyone reads this... if you ever take that compression bolt off, replace it! Also don't be afraid of recycled parts, they save a ton of money.

Always glad to help out a fellow M5 owner when I can

[technician117]

Originally Posted by SuperF10

This post is 4 months old, you're right on the money. I replaced my hub and reused the compression bolt like a dummy.

The dealer wanted like $4k+ to do the work. I got a salvage shaft for $275 shipped to my house off a totaled M5 that only had 15k miles, bought a new OE hub for ~$370 and then replaced basically all of the mounting hardware for the rear suspension while I was down there. All in all it was less than $1k. The repairs have held up great, I have put about 5k miles on the car since and no issues.

If anyone reads this... if you ever take that compression bolt off, replace it! Also don't be afraid of recycled parts, they save a ton of money.

Great follow up. Thanks for posting an update. I assume you tried to get it fixed through your warranty first though, right?

And I agree - there are plenty of items that are good/fine to buy used. I had the passenger mirror broken off by someone overnight last year. Insurance paid out for a new mirror, roughly $2,600 just for the mirror parts. I bought a correct part number used one from a salvage yard on eBay for less than $500 and had the cap painted for cheap.

[SuperF10]

Originally Posted by technician117

Great follow up. Thanks for posting an update. I assume you tried to get it fixed through your warranty first though, right?

And I agree - there are plenty of items that are good/fine to buy used. I had the passenger mirror broken off by someone overnight last year. Insurance paid out for a new mirror, roughly $2,600 just for the mirror parts. I bought a correct part number used one from a salvage yard on eBay for less than $500 and had the cap painted for cheap.

Yes, it was actually the first time my warranty company has denied something. They stated that because the bolt failed they were not responsible for the parts that ended up damaged or something like that. I didn't really push it because I was the one who damaged the vehicle.

I'm an adjuster at a major carrier and I deal with sourcing used parts all day as part of my job. I think there is just a negative attitude towards the word "used". In reality you are buying a part that is OE and basically guaranteed to have perfect fitment. We use the term "Quality Recycled" and instead of saying "cheapest" we say "most cost-effective". LOL