Pinion Seal Rear Differential

[t44tq]

Are there any "while you're in there" jobs that should be done if I'm doing the pinion seal? My diff looks like it's leaking from the pinion seal.

I believe the driveshaft has to be removed to do that job, so I'm thinking I should do the flex disc and a fluid change for the diff. Anything else?

Thanks!

[Arith2]

Driveshaft work since it will be out. Maybe change the CSB but they last for years. It's not worth the effort if it's recently been done

[old///MFanatic]

I would really consider (depending on miles/condition) the front diff bushing while having easy access. The rear diff bushings are easier. Although unfortunately they’re part of a new diff cover for the rear.
Go OE for the front bushing and rear even if poly sounds cooler.

[bigjae46]

I would repack the CV with grease. Inspect the flex disc and center bearing. Make sure you have a new CV gasket (or 2 in case you screw one up).

[Cubieman]

I would repack the CV with grease. Inspect the flex disc and center bearing. Make sure you have a new CV gasket (or 2 in case you screw one up).

Would you recommend going with the factory recommend stuff ( 83190447919 ) or simply grab from some CV grease from the parts store?

Also, on a side note, the CSB, does this require a press to install? I have a new CSB and everything is disassembled laying on a bench so I kind would like to replace but do not have a press. Looking for an excuse to buy one though.

Like OP, also wanting to due pinion seal while diff is out, but it's not leaking very much if at all (what I see may be CV grease slinging out) and I don't to have the job snowball into a full diff rebuild if the pinion nut is over-tightened.
Might just have to max it to the max and go for it..lol.

[t44tq]

I would repack the CV with grease. Inspect the flex disc and center bearing. Make sure you have a new CV gasket (or 2 in case you screw one up).

You're talking about the rear axle CV joints?

Does the diff need to come out of the car to do the pinion seal?

I ordered a new flex disc, bushing and hardware, so if the flex disc needs to be done, I'll have the parts ready to go. Also ordered the Corteco improved pinion seal.

The rest, if there are any other parts needed, hopefully my mechanic can get easily. With supply chain issues, I'm kind of paranoid about not being able to get parts these days.

[t44tq]

I would really consider (depending on miles/condition) the front diff bushing while having easy access. The rear diff bushings are easier. Although unfortunately they’re part of a new diff cover for the rear.
Go OE for the front bushing and rear even if poly sounds cooler.

Does the diff need to come out of the car to do the pinion seal? I didn't think so, but I don't know?

So there are three diff bushings in the M3?

[Cubieman]

Does the diff need to come out of the car to do the pinion seal? I didn't think so, but I don't know?

So there are three diff bushings in the M3?

Diff. could stay in for pinion seal I would imagine, and yes 3 bushings, 2 in the rear and 1 in the front. The front bushing is on the right hand (pass. side) towards the front/bottom portion of the diff.

Edit: Here is my diff., in red is the female threaded portion for the front diff. bushing.

[Atreezy]

I'm doing some work in the back and while I had the diff out I was thinking of replacing the input and output seals. Does anyone know if simply changing these seals is going to alter the internal backlash?
(For the input side I understand marking the nut and counting rotations.)

[WoGGo]

Make sure you have a new CV gasket (or 2 in case you screw one up).

If you've just replaced the CV/gasket and not even put 150 miles on it, would you still recommend to replace?

[bigjae46]

Would you recommend going with the factory recommend stuff ( 83190447919 ) or simply grab from some CV grease from the parts store?

Also, on a side note, the CSB, does this require a press to install? I have a new CSB and everything is disassembled laying on a bench so I kind would like to replace but do not have a press. Looking for an excuse to buy one though.

Like OP, also wanting to due pinion seal while diff is out, but it's not leaking very much if at all (what I see may be CV grease slinging out) and I don't to have the job snowball into a full diff rebuild if the pinion nut is over-tightened.
Might just have to max it to the max and go for it..lol.

I used liqui-moly CV grease.

I don’t think you need a press. Maybe a 3 jaw puller.


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[bigjae46]

You're talking about the rear axle CV joints?

Does the diff need to come out of the car to do the pinion seal?

I ordered a new flex disc, bushing and hardware, so if the flex disc needs to be done, I'll have the parts ready to go. Also ordered the Corteco improved pinion seal.

The rest, if there are any other parts needed, hopefully my mechanic can get easily. With supply chain issues, I'm kind of paranoid about not being able to get parts these days.

No, the driveshaft CV. But you could also repack the half shafts. Especially the inner driver CV which takes a lot of heat from the exhaust.

Diff can stay in the car for the pinion seal.

Replacing the seals does not affect backlash. Only the pinion seal may affect pinion bearing preload which may accelerate wear on the pinion bearings.

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[bigjae46]

If you've just replaced the CV/gasket and not even put 150 miles on it, would you still recommend to replace?

Yes. You’ll likely destroy it separating the driveshaft CV from the diff.


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[t44tq]

Thanks- I dropped the car off at the mechanic, so he'll take care of the job. I ordered the "improved" Corteco pinion seal, as that is most likely not a normal item. Also a new flex disc and hardware (I'm picky about the source of a lot of rubber parts these days)- the rest, he can supply.

[WoGGo]

Yes. You’ll likely destroy it separating the driveshaft CV from the diff.

Also, to get access to the "nut", would you need to remove then entire drive shaft from the flex disc, or can you just uncouple the CV from the diff and have it suspended out of the way?