Can't find my clunk 128i

[Blau]

On gear shifts I occasionally hear a clunk sound from somewhere in the rear end. It's hit or miss as to when it happens. I thought it was a faulty drive shaft because my old one had an issue accepting a new CSB and I think the splines got junked. I figured it was coming from the telescoping part of the two shafts. I picked up a new one from Texas Driveshaft Specialist. It has an adjustable preload locking center, which I loosend to let the shaft reach both the trans and the diff, then tightened down. Upon my shake down drive, the clunk went away. About 12 hours later, it's back. It's much fainter that it was before, but it's still there.

Any idea where it could be coming from? I preloaded the CSB and torqued down the bolts. The driveshaft was torqued to the brand new giubo and differential.

Should the shaft be allowed to "telescope"?

Other things that might be important to know:

Brand new OEM motor mounts
New shaft, giubo, and CSB
All rear suspension arms and bushings are tight, there is no play on any of the arms
Newish poly diff and RSFB
Single mass flywheel and matching clutch
Bilstein coilovers

Clunk happens on gear changes. Sometimes up shifting and sometimes downshifting.

Any help would be greatly appreciated.

[WrathOTM]

Hmm.. I got a clunk after doing poly bushings on the diff mount points. And it seems to be worse in the cold. You have a couple of the things I would mention, maybe the center bearing wasn't lined up right perhaps?

[spidertri]

Poly diff bushing is the flag to me. There's always a small amount of backlash between the pinion and ring gear. When you unload/load the driveline during gear changes that metal on metal is being transmitted through.

[Blau]

Originally Posted by spidertri

Poly diff bushing is the flag to me. There's always a small amount of backlash between the pinion and ring gear. When you unload/load the driveline during gear changes that metal on metal is being transmitted through.

This problem probably started about when I did poly diff and RSFB... I do wonder if that's it.

This might make me feel a little less anxious about it. My cousin recommended I just turn up the radio...

[acidstrawbz]

Dude, Ive literally had the EXACT same problem. Ive done EVERYTHING. I serviced driveshaft, greased center splines connecting the two halves together, new CSB, new Guibo, new carrier bushing, new poly diff bushings. Fluid flush. Still present. Drives me nuts. Otherwise the car runs perfectly!!!

Turning up radio does not solve problem, knowing its there bothers me. If you ever figure it out please update thread. I will do same. Are you SURE its coming from diff and not transmission?

[Blau]

Originally Posted by acidstrawbz

Dude, Ive literally had the EXACT same problem. Ive done EVERYTHING. I serviced driveshaft, greased center splines connecting the two halves together, new CSB, new Guibo, new carrier bushing, new poly diff bushings. Fluid flush. Still present. Drives me nuts. Otherwise the car runs perfectly!!!

Turning up radio does not solve problem, knowing its there bothers me. If you ever figure it out please update thread. I will do same. Are you SURE its coming from diff and not transmission?

I have eliminated the clunk... Mostly.

I'm not certain it was one thing, but rather a few things coming together. I bought a new driveshaft, csb, guibo, motor mounts, transmission mounts, new guibo bolts, new driveshaft to diff bolts... Lol. A lot of bullshit stuff. There is sometimes a very faint clunk when I back out of my steep driveway. But I am now pretty confident that the clunk isn't anything scary. I've gone over every bolt, replaced damn near everything in the drive line.

On a side note, poly trans mounts were an absolute disaster. 0/10 would not recommend for a street car. OEM motor and transmission mounts feel lovely. Mine had 150k on them. The car feels so much smoother now.

[acidstrawbz]

Originally Posted by Blau

I have eliminated the clunk... Mostly.

I'm not certain it was one thing, but rather a few things coming together. I bought a new driveshaft, csb, guibo, motor mounts, transmission mounts, new guibo bolts, new driveshaft to diff bolts... Lol. A lot of bullshit stuff. There is sometimes a very faint clunk when I back out of my steep driveway. But I am now pretty confident that the clunk isn't anything scary. I've gone over every bolt, replaced damn near everything in the drive line.

On a side note, poly trans mounts were an absolute disaster. 0/10 would not recommend for a street car. OEM motor and transmission mounts feel lovely. Mine had 150k on them. The car feels so much smoother now.

After more and more research, I came across a BMW bulletin describing the differential input flange becoming dry and or mating surfaces with the driveshaft causing my issues. I decided to buy a whole entire remanufactured differential for $400 versus the labor to pull diff, and regrease input flange + new seals which would be more than a reman diff...

Going in for service to my indy this weekend. He said he will disconnect the driveshaft from diff and roll the car to see if he can recreate the noise or not to confirm if it's the diff or not. Hopefully this fixes it. I am at my end and so is my girlfriend of hearing about it lol. If this doesnt remedy the problem, i stg I am buying a honda civic lol nah but in reality if it continues I will probably also eventually buy a new driveshaft... Which one did you go with by the way? OEM ($$$)? Pull off a wrecked car? Custom?

Also, is the clunk noise still gone? What about when youre in low gear at a high rpm 5k+, and let off throttle completely? Still no noise?

Here is the service bulletin description:

SI B33 04 08
Rear Axle
August 2009
Technical Service
This Service Information bulletin supersedes SI B33 04 09 dated October 2008.
[NEW] designates changes to this revision
The differential input flange mating surface with the input drive pinion is insufficiently greased.
E82 and E88 (1 Series), all models
E85 and E86 (Z4), all models
E60 and E61 (5 Series), all models
E63 and E64 (6 Series), all models
E65 and E66 (7 Series), all models
E90, E91, E92 and E93 (3 Series), all models
The customer complains that a single cracking or clicking noise can be heard from the rear of the vehicle while engaging a drive gear, releasing the clutch, during load reversal (shifting from reverse to drive, etc.), or when accelerating from a stationary position.
This is not a failure of the differential assembly. Do not replace the complete differential.
Remove the differential drive flange in accordance with Repair Instruction RA 33 11 021. Apply lubricant [NEW] P/N 83 23 0 443 864 on the input flange mating surface (1), as described in the illustration.
Before complete reassembly. replace the input flange seal and collar nut retaining plate as described in RA 33 01 021. Refer to the EPC for correct part numbers, based on model.

[Blau]

Originally Posted by acidstrawbz

After more and more research, I came across a BMW bulletin describing the differential input flange becoming dry and or mating surfaces with the driveshaft causing my issues. I decided to buy a whole entire remanufactured differential for $400 versus the labor to pull diff, and regrease input flange + new seals which would be more than a reman diff...

Going in for service to my indy this weekend. He said he will disconnect the driveshaft from diff and roll the car to see if he can recreate the noise or not to confirm if it's the diff or not. Hopefully this fixes it. I am at my end and so is my girlfriend of hearing about it lol. If this doesnt remedy the problem, i stg I am buying a honda civic lol nah but in reality if it continues I will probably also eventually buy a new driveshaft... Which one did you go with by the way? OEM ($$$)? Pull off a wrecked car? Custom?

Also, is the clunk noise still gone? What about when youre in low gear at a high rpm 5k+, and let off throttle completely? Still no noise?

Here is the service bulletin description:

SI B33 04 08
Rear Axle
August 2009
Technical Service
This Service Information bulletin supersedes SI B33 04 09 dated October 2008.
[NEW] designates changes to this revision
The differential input flange mating surface with the input drive pinion is insufficiently greased.
E82 and E88 (1 Series), all models
E85 and E86 (Z4), all models
E60 and E61 (5 Series), all models
E63 and E64 (6 Series), all models
E65 and E66 (7 Series), all models
E90, E91, E92 and E93 (3 Series), all models
The [...]

I will look into this bulletin. It seems like that may have been a part of this journey.

Pulling the diff flange off is not hard. Pulling the entire diff off the subframe is also not hard. Hardest part is removing your exhaust if you live in a rust belt state.

I got my driveshaft from Texas Driveshaft Specialist. It was under $600. I'm happy with it, but it wasn't the cure to the dreaded clunk.

The noise is mostly gone, but when it was happening, it happened going into reverse, starting from a stop, or after hard shifts from 1-2, 2-3, and 3-4. Most of the time it was from 2-3.

Don't buy a Honda Civic. Cover all your bases and if it's still there just turn the music up, buy a louder exhaust, and enjoy the car.

If the clunk stuff starts back up I'll follow the bulletin advice. It seems like an easy enough fix.

Best of luck!