rear diff bushing crack

[Austin_M4]

Hello, I went through forum but could not find this issue, hope its not been covered already.

When having the car on lift, I noticed a leakage on rear subframe near rear diff bushing mount. Under closer inspection, cracks were found on rear diff bushing, bushing is probably filled with hydraulic oil for vibration dampening, maybe that is the reason for oil leakage.
As the car has rear subframe bolted directly to chassis there must be high loads on the bushing and unfortunately at the rear differential is mounted only on one bushing.

Is there a reliable solution to prevent this, e.g. Powerflex bushing kit or conversion bracket to double mounted rear differential ? I am not sure if the bracket will fit through diff locking servomotor.

Any input appreciated.

[jww///95]

Historically bmw diffs had one front mount and two rears. F8x platform has flipped that with two front mounts and one rear. Presumably, this would reduce the "torquing" effect of the diff relative to the subframe under load which was usually rough on the single front mounts.

Based on your pics as well as the price of the lone rear mount i suspect you're correct that it's fluid filled and replacing will probably stink given the location unless there are some creative special service tools bmw has employed for this one... check ista for details on that one.

I'd also be included to talk to bimmerworld, turner, maxpsi etc to see failure rates on the bushings for track, strip, or big power cars. Wondering if you might have just had a bad bushing so swap it like for like and go forward. Might also explain why your search didn't produce any similar experiences on the forum.

The knock on the higher durometer bushings is diff noise/whine entering the cabin. I'm guessing that's the major reason for the fluid filled factory spec part. If you go with poly expect to be annoyed for a street car.

Not a lot of help on this one but hopefully there's some worthwhile council here.

[Halim@HCP]

Had the same on my M3 F80. Had diff replaced and ofcourse this got renewed.

[CAOZKAN]

Originally Posted by Austin_M4

Hello, I went through forum but could not find this issue, hope its not been covered already.

When having the car on lift, I noticed a leakage on rear subframe near rear diff bushing mount. Under closer inspection, cracks were found on rear diff bushing, bushing is probably filled with hydraulic oil for vibration dampening, maybe that is the reason for oil leakage.
As the car has rear subframe bolted directly to chassis there must be high loads on the bushing and unfortunately at the rear differential is mounted only on one bushing.

Is there a reliable solution to prevent this, e.g. Powerflex bushing kit or conversion bracket to double mounted rear differential ? I am not sure if the bracket will fit through diff locking servomotor.

Any input appreciated.

I didn't have the leakage but my bushing was cracked as well. I replaced it with powerflex black series without knowing it was cracked. So far I'm happy with it.

[mandukamja]

how long did this fix take you? Was it DIY? my F80 has been at the dealership over a week now as they are saying it is a big job...

[ruley74]

I noticed mine cracked also, curious to see what path you go.

[DataNerd]

Mine cracked as well. BMW replaced it under warranty. This was a while ago, but I wanna say it would have been ~$800 if not covered.

I only noticed it due to vibration in the steering wheel under acceleration.

[Greg FEightytwo]

Originally Posted by CAOZKAN

I didn't have the leakage but my bushing was cracked as well. I replaced it with powerflex black series without knowing it was cracked. So far I'm happy with it.

did you do the front ones as well as the back one? Mines cracked at 37k miles and now its got a crack on both sides. I saw there is one for the back and few in the front.

[CAOZKAN]

Originally Posted by Greg FEightytwo

did you do the front ones as well as the back one? Mines cracked at 37k miles and now its got a crack on both sides. I saw there is one for the back and few in the front.

I changed all the bushings with powerflex black series. I must say it made a lot of difference when it comes to steering feedback and body roll as well as power delivery through the differential. However, coupled with KW CS2 the ride became definitely harsher. To me, it's still tolerable, I drive my car as daily without any complaints

[Greg FEightytwo]

Originally Posted by CAOZKAN

I changed all the bushings with powerflex black series. I must say it made a lot of difference when it comes to steering feedback and body roll as well as power delivery through the differential. However, coupled with KW CS2 the ride became definitely harsher. To me, it's still tolerable, I drive my car as daily without any complaints

good to hear. mine is set up for track only with kw cs3 ways and spherical bearings so it rides great on track and harsh on street. these are the only bushings i didnt change 😿

[CAOZKAN]

Originally Posted by Greg FEightytwo

good to hear. mine is set up for track only with kw cs3 ways and spherical bearings so it rides great on track and harsh on street. these are the only bushings i didnt change 😿

Better change them my friend because they aren't strong enough to hold more than 1-2 track season

[TurboM]

Originally Posted by CAOZKAN

Better change them my friend because they aren't strong enough to hold more than 1-2 track season

That's pretty lame. I'm sure this issue is fairly isolated but every part on these cars should hold a lot more than that without issues given that's what it was designed for.

[CAOZKAN]

Originally Posted by TurboM

That's pretty lame. I'm sure this issue is fairly isolated but every part on these cars should hold a lot more than that without issues given that's what it was designed for.

I'm writing based on my experience and few other cars, but it can also be related to our roads bad condition as well. However the parts which was replaced with the new aftermarket ones looked very abused and in bad condition. My car had 55k miles on it when this happened.(I think this might be an useful information as well )

[MPOOR]

Originally Posted by CAOZKAN

I changed all the bushings with powerflex black series. I must say it made a lot of difference when it comes to steering feedback and body roll as well as power delivery through the differential. However, coupled with KW CS2 the ride became definitely harsher. To me, it's still tolerable, I drive my car as daily without any complaints

I'm after the same stuff ~!! Glad to hear powerflex black series bushings increased drivetrain performance. !!! No need comfort for my car so ~

[Redline10000]

I blew mine out after one season of Autox and track. How long was the install of the powerflex bushing.

[ruley74]

Had a service last Friday and they noted it.... Quoted my 1500 AUD for the replacement!!!

[Redline10000]

Has anyone done this themselves? I’m trying to figure out if it’s possible to replace the bushing without dropping the whole diff. Dealing with the driveshaft seems like a PITA. Lots of special tools needed.

[CAOZKAN]

Originally Posted by Redline10000

I blew mine out after one season of Autox and track. How long was the install of the powerflex bushing.

It took 3-4h for my mechanics to install it.

[Redline10000]

Originally Posted by CAOZKAN

It took 3-4h for my mechanics to install it.

Do you know if they had to disconnect the driveshaft?

[CAOZKAN]

Originally Posted by Redline10000

Do you know if they had to disconnect the driveshaft?

Yes they needed to do that

[Brasko]

Might as well do a front diff bushings if you're at it.

[Geez3]

42k miles and cracking, was noticed on my last inspection.

Not sure if I'm going to tackle this switch of these busing or not. Not sure if they are pressed into the diff or will they pull out with a screwdriver and a little patience.

Any brave soldiers already tackle this?