Help needed with rear axle diff noise

[noclue1]

Hello,
I have a metallic clunking noise from the car while driving which I do not understand where it is coming from.

I bought the car with a broken rear diff mount and intermediate axle, replaced the parts and the car has been fine. For information, the mount was used, but with low km.
Got a bad clunk sound a while ago from the rear, slack in both cv shafts. Replaced both shafts, probably 50km on them now.

But there's still a sound behind it that I don't understand what's coming from.
- The sound comes when starting from a standstill, it doesn't matter if you turn to the right or left.
- It also comes when driving on speed dumps or some uneven road sometimes
- The sound is also there when I put it in manual mode and release the gas, then I give a little gas and it is there

I can't imagine that there should be something inside the diff, because then there should have been noises constantly and not just on a few occasions. Could it be that there are bad diff mounts, will it make such a sound?

I am attaching a link to my YouTube channel where I have uploaded videos of the sound. Username on account is M5F10M5 - M5 F10 rear axle noise

Appreciate all help and suggestions.

www.youtube.com/@M5F10M5

[M5Rick]

Your car is a Competition? What do you mean by 'intermediate' axle.

[M5_Raz]

Could be a cracked diff mount that flexes as you put power into it and drive away. I would drive very carefully until it’s resolved.

[KurtsM5]

Originally Posted by M5Rick

Your car is a Competition? What do you mean by 'intermediate' axle.

The BMW F10/F11/F07/F18 is the sixth generation of the BMW 5 Series, which was manufactured for model years 2010–2017.[11][12] The body styles of the range are:

4-door sedan/saloon (F10)
5-door estate/wagon (F11, marketed as "Touring")

His signature says F11.

[M5Rick]

Originally Posted by KurtsM5

The BMW F10/F11/F07/F18 is the sixth generation of the BMW 5 Series, which was manufactured for model years 2010–2017.[11][12] The body styles of the range are:

4-door sedan/saloon (F10)
5-door estate/wagon (F11, marketed as "Touring")

His signature says F11.

I know but the vids that relate to the problem are of an F10 saloon that looks like a Competition with those 601M wheels and the Comp's have a different rear axle ratio to standard M5's which is why I'm asking him if it is one.

[KurtsM5]

Originally Posted by M5Rick

I know but the vids that relate to the problem are of an F10 saloon that looks like a Competition with those 601M wheels and the Comp's have a different rear axle ratio to standard M5's which is why I'm asking him if it is one.

Didn't know that. I've never seen one, don't think they sold them in the US.

[KurtsM5]

Originally Posted by M5_Raz

Could be a cracked diff mount that flexes as you put power into it and drive away. I would drive very carefully until it’s resolved.

I'd call a tow truck.

[M5Rick]

So what I understand is a second hand diff carrier was fitted and it's likely that this one could have developed a crack also, I want to know if the original diff was replaced also...the plot thickens

[M5Rick]

Originally Posted by KurtsM5

Didn't know that. I've never seen one, don't think they sold them in the US.

Yup they are in the US also, quicker steering, 1cm lower suspension, higher geared diff, recalibrated injection giving 575 hp as opposed to 560 for the non comp.

[noclue1]

Originally Posted by M5Rick

Your car is a Competition? What do you mean by 'intermediate' axle.

The driveshaft from gearbox to the diff.
I just got the 601M wheels, not a competition car

[noclue1]

Originally Posted by M5_Raz

Could be a cracked diff mount that flexes as you put power into it and drive away. I would drive very carefully until it’s resolved.

The diff mount and driveshaft was broken and was changed, my wife has been driven the car since then to work and home. No pulls at all.

[noclue1]

Originally Posted by KurtsM5

The BMW F10/F11/F07/F18 is the sixth generation of the BMW 5 Series, which was manufactured for model years 2010–2017.[11][12] The body styles of the range are:

4-door sedan/saloon (F10)
5-door estate/wagon (F11, marketed as "Touring")

His signature says F11.

Bro i have probably had 20 cars since that F11, signature has not been changed.

[noclue1]

Originally Posted by M5Rick

So what I understand is a second hand diff carrier was fitted and it's likely that this one could have developed a crack also, I want to know if the original diff was replaced also...the plot thickens

The diff was not changed. I doubt that is is the diff since the sound is not constand there, maybe it should have been somekind of grinding or something all the time if it was the diff?

It is very weird if the mount has cracked again since the car has only been driven 3000km since then by my wife wich drives really slow. They could not see anything when when both cv axles was changed. Will check again.

[M5Rick]

Originally Posted by noclue1

The diff was not changed. I doubt that is is the diff since the sound is not constand there, maybe it should have been somekind of grinding or something all the time if it was the diff?

It is very weird if the mount has cracked again since the car has only been driven 3000km since then by my wife wich drives really slow. They could not see anything when when both cv axles was changed. Will check again.

Yes no way a worn out diff would sound like that. Both d/shafts were replaced with second hand ones? If the carrier is ok then it sounds to me now more like a struggling cv joint when drive is taken up.

[M5Rick]

Or UJ (universal joint) like they are called also, may feel alright working it by hand before fitting but different with 560 hp going through it.

[noclue1]

Originally Posted by M5Rick

Yes no way a worn out diff would sound like that. Both d/shafts were replaced with second hand ones? If the carrier is ok then it sounds to me now more like a struggling cv joint when drive is taken up.

Both output shafts as BMW call them are replaced with brand new ones. Not org, but new.

Partnr: 33212284115 / 33212284116

The ting i discovered today is that the sound does not appear when reversing, i tested i in reverse maybe 20 times today. Only in drive

[M5Rick]

Originally Posted by noclue1

Both output shafts as BMW call them are replaced with brand new ones. Not org, but new.

Partnr: 33212284115 / 33212284116

The ting i discovered today is that the sound does not appear when reversing, i tested i in reverse maybe 20 times today. Only in drive

I'd put it on a rolling road with a mechanic each side to try to pin point it closer, that's all I can suggest for now

[noclue1]

Originally Posted by M5Rick

I'd put it on a rolling road with a mechanic each side to try to pin point it closer, that's all I can suggest for now

The noise has finally been located, it is coming from the rear diff mount. We had the car on a ramp while i sat in it pressed the brake and gas to provoke the sound.

First thing we did, retighten the bolt. Did not help.

Second thing, got the bolt loose and the diff can be moved slight upwards. Pushed it up and tightened the bolt, noise gone for a couple of days but came back. I think it slowly got down because of the force.
Looked at ista for rep guide, it clearly states that the diff should be lowered while tightening.

Third thing, new bolt and nut. Followed instructions and the noise is still there, did not help at all.

Im really out of ideas on this one...

[M5Rick]

Originally Posted by noclue1

The noise has finally been located, it is coming from the rear diff mount. We had the car on a ramp while i sat in it pressed the brake and gas to provoke the sound.

First thing we did, retighten the bolt. Did not help.

Second thing, got the bolt loose and the diff can be moved slight upwards. Pushed it up and tightened the bolt, noise gone for a couple of days but came back. I think it slowly got down because of the force.
Looked at ista for rep guide, it clearly states that the diff should be lowered while tightening.

Third thing, new bolt and nut. Followed instructions and the noise is still there, did not help at all.

Im really out of ideas on this one...

You've already replaced the holder so like you I'm out of ideas, could it be a suspension arm bush in the multi link set up..