Diff Output Shaft Seal DIY

[Cerb321]

Hey everyone,

Recently acquired an '05 M3 with 28k miles on it. Have done a few maintenance items already but still have a few pending. My diff's output shaft seal has a small leak, and I got a quote for $1100 to replace it, majority of it being labor. Was wondering if anyone has any DIY guides they’d recommend / have used. I’ve found 2 or 3 guides that are pretty decent but was wondering if there are any better ones out there. Or if it's just worth paying the shop to do it.

[simon_c]

Make sure to do the pinion seal as well.

[Flow]

$1100 for a diff out shaft seal ! That's steep in my opinion.
If it's the right side you don't even need to drop the exhaust.
Simply unbolt the output shaft, remove the output flange of the diff, replace the seal and re install everything.
Quite a simple job IMO.
Input shat seal and left side are a bit more involved as you need to remove the exhaust, and you have to know what you're doing to re-torque the input shaft bolt.

[sapote]

Hey everyone,

Recently acquired an '05 M3 with 28k miles on it.

I think it's V2 Diff, so the leaking is likely on the left shorter output flange. Try to DIY as it should NOT be hard just to replace the seal.
Are you sure the low mieage seal leaking or it's from the top vent hole?

Edited: should NOT

[bigjae46]

Small leak...not sure I'd rush to do it.

If you do, I'd consider getting the inner shaft CV boot replaced and repacked with grease. Relatively easy to do if the axle is already removed.

[YYZ-M3]

I just had my pinion seal done. $900 plus tax Canadian at BMW dealer. Did guibo at the same time.

[Cerb321]

$1100 for a diff out shaft seal ! That's steep in my opinion.
If it's the right side you don't even need to drop the exhaust.
Simply unbolt the output shaft, remove the output flange of the diff, replace the seal and re install everything.
Quite a simple job IMO.
Input shat seal and left side are a bit more involved as you need to remove the exhaust, and you have to know what you're doing to re-torque the input shaft bolt.

Yeah, seems fairly straightforward and not worth the labor charge. Hardest part looks to be seating the seal properly. Appreciate the reply!

[Cerb321]

I think it's V2 Diff, so the leaking is likely on the left shorter output flange. Try to DIY as it should NOT be hard just to replace the seal.
Are you sure the low mieage seal leaking or it's from the top vent hole?

Edited: should NOT

Pretty sure it's from the seal. I noticed it upon delivery of the car, and the shop I took it to for a few other items confirmed it.

[Cerb321]

Small leak...not sure I'd rush to do it.

If you do, I'd consider getting the inner shaft CV boot replaced and repacked with grease. Relatively easy to do if the axle is already removed.

Yeah, it's very small. Just seeping a bit from the seal, nothing on my garage floors or anything. If it's not something I should fix in the near future, I was thinking of just holding off until one of the other seals goes bad to just do a full reseal of the diff.

[jayjaya29]

I'd leave it until it starts leaking more.

[davidf]

Fairly common that M3's have a thick coating of greasy dirt covering the diff due to this type of leak. I would go ahead and drop the diff and repack the clutch pack and install an anti clunk washer while resealing the entire diff. It is not going to fix itself.

[bigjae46]

. I would go ahead and drop the diff and repack the clutch pack and install an anti clunk washer while resealing the entire diff.

Repack? Or replace? Would be tragic if someone repacked the LSD with grease.

[Flow]

Fairly common that M3's have a thick coating of greasy dirt covering the diff due to this type of leak. I would go ahead and drop the diff and repack the clutch pack and install an anti clunk washer while resealing the entire diff. It is not going to fix itself.

That is an entirely different project !
The « while in there » gone wrong

[davidf]

Repack? Or replace? Would be tragic if someone repacked the LSD with grease.

Repack/replace with new friction and steels. Backlash between ring and pinion is not changed while doing so which makes it a parts replacement exercise.

[sapote]

I would go ahead and drop the diff and repack the clutch pack and install an anti clunk washer while resealing the entire diff..

I wouldn't touch the clutch pack or adding the concave washer; the car has only 28K miles.