Look inside of a diff that had the M Clunk

[bmwfnatic]

https://youtube.com/shorts/JF3N1MsaB_8?feature=share

Do not. There is a bump on the backside. It’s a blind hole.


Sent from my iPhone using Tapatalk

Can't view the video, says it is private

Edit: I can see it now, for reference I am talking about the 2 holes on each side that are towards the rear of the car when the diff is in the installed position, they go all the way trough, can even be seen on your video.

[mrgizmo04]

Yes, the 2 (per side) closest to the rear cover run through the case (red lines). The ones circled in blue are the bumps for the other 6 (per side) that don't run all the way through.


Sent from my SM-G950U using Tapatalk

[SQ13]

Diff or LSD carrier only?

Actually, I enjoy rebuilding these.


Sent from my iPhone using Tapatalk

Me too. Diff is fucked and I’m local. 😅

[sapote]

The spider gears had play. Likely due to the wear in the clutch plates causing more clearance. More clearance in the clutch packs creates more backlash in the spider gears which will cause a clunk noise when taking off from a stop.

You can see wear on the large spider gear

The plays or backlash between the larger side-gears and the smaller 4 spider gears is not affected by the condition of the clutch stack, new or old worn. The only way to reduce the plays is to shim one of the side-gear inward (the RH side in this case, and the LH side for version 2 diff).
Even when brand new these gears were set to have certain amount of plays – it seems to be too much for what it is but I don’t know why. This amount of plays does not cause the clunk by itself, but only when the clutch stack slip jerkily especially when start moving from stop.

Why old worn clutch stack seems to cause more M clunk? The clutches slip cause the side-gear to accelerate and hit the spiders hard.


The marks on the gear faces probably due to the side-gears hammering the spiders whenever the clunk happened.

[bigjae46]

Yes, the 2 (per side) closest to the rear cover run through the case (red lines). The ones circled in blue are the bumps for the other 6 (per side) that don't run all the way through.


Sent from my SM-G950U using Tapatalk

Lol…I never noticed that!

Still, diff fluid doesn’t sit there so I wouldn’t bother applying any sealant to the bolts.


Sent from my iPhone using Tapatalk

[Cubieman]

Lol…I never noticed that!

Still, diff fluid doesn’t sit there so I wouldn’t bother applying any sealant to the bolts.


Sent from my iPhone using Tapatalk

What torque spec do you use and which loctite if not sealant, blue 243? I'll be doing seals tonight.

Also, must you use a new pinion nut "securing plate" ( 33121205138 ) if removing nut to replace input seal?

[fattycharged]

Diff or LSD carrier only?

Actually, I enjoy rebuilding these.


Sent from my iPhone using Tapatalk

TBD, I need to pull it and replace with the spare, I just happen to be in Houston

[bigjae46]

What torque spec do you use and which loctite if not sealant, blue 243? I'll be doing seals tonight.

Also, must you use a new pinion nut "securing plate" ( 33121205138 ) if removing nut to replace input seal?

I run them in with a small impact with no loctite or sealant.

I supposed you could get the plate out without messing it up. I pry it out with a screwdriver.

You should inspect the threads on the pinion nut. The threads on the nut can strip.


Sent from my iPhone using Tapatalk

[Tonggi]

Im not gonna lie, after doing my Vince Bar install. My m clunk is SUPER PRONOUNCED, it has me scared that something is loose. I had all solid bushings before on my first M (8+ years ago so I completely forgot how it felt but I dont remember it like this) The following items were done

1. CMP Subframe bushings
2. Condor Poly Diff Bushings
3. Turner Upper Rear bearings
4. All oem Outer Upper and Lower Bearings replaced
5. Turner Street Adjustable Rear Control Arms


Guido = Stock (Fresh 8k miles)
Poly Motor and Trans Mount
Stock Center Bearing (might change this now)

[oceansize]

Im not gonna lie, after doing my Vince Bar install. My m clunk is SUPER PRONOUNCED, it has me scared that something is loose. I had all solid bushings before on my first M (8+ years ago so I completely forgot how it felt but I dont remember it like this) The following items were done

1. CMP Subframe bushings
2. Condor Poly Diff Bushings
3. Turner Upper Rear bearings
4. All oem Outer Upper and Lower Bearings replaced
5. Turner Street Adjustable Rear Control Arms


Guido = Stock (Fresh 8k miles)
Poly Motor and Trans Mount
Stock Center Bearing (might change this now)

Yeah all that poly is gonna make a ruckus, as you know. You've removed all drive train slop except the m-clunk which makes it even more noticeable.... I'm assuming you have a track car so it doesn't really matter.

[Tonggi]

Yeah all that poly is gonna make a ruckus, as you know. You've removed all drive train slop except the m-clunk which makes it even more noticeable.... I'm assuming you have a track car so it doesn't really matter.

I didnt want to buy a new oem diff plate for the oem bushings. Its a weekend car. I dont commute with it, track events in future are possible but not a track build. I might need to get oem bushings if i check that everything si tight or live with the clunk

[lemoose]

Guido = Stock (Fresh 8k miles)

like this?

[scmtx]

Just my .02, I had plenty of play in my diff with 140k on it. So...I ordered the shim kit...couldn't find anyone who wanted to rebuild it. I became impatient (all my bushing are poly and the noises drove me crazy) and ordered a replacement from Diffs Online. I removed and replaced the old with new....which has less play, slack in the spider gears. First drive....still have plenty of driveline noise.
Had I known someone like Jae MIGHT have been willing to rebuild what I have, I would have been much happier. The play on the passenger axle stub? is/was causing most of my issues/noises.

[sapote]

The play on the passenger axle stub? is/was causing most of my issues/noises.

Actually the plays on the left side spider/side-gear caused the clunk, not the right side. The carrier turned the left output flange splines (via the clutch stack inner splines) directly first, not the spiders/side gears, and then the clutch slipped at higher load, and the spiders whacked the left side-gear hard to cause the clunk. During the time before the clunk, the right side was trailing along with no drive force, and so its side-gear was resting against the spiders with zero plays (if the wheel is faster than the car then the side gear is ahead of the spiders and with max plays between them, but this cannot be the case before acceleration).

[Tonggi]

like this?

AYOOOOO GTL BABEHH

lmao good to know that a new diff won't fix my issue. so I will just inspect it and drive this puppy till it implodes on its own