Pinion seal replacement + diff fluid question

[bigjae46]

New to this forum.. at least posting in here but is there any specific way to install the driveshaft back on the car after you replace the pinion seal? Pre-loading it or something?

Not backwards....lol.

I have never had to push the CSB forward, it always sits forward on the studs. Not sure if I am just really lucky.

Have an extra CV joint gasket handy...or two. They are easy to mess up. Also a good time to pack the CV with a little more grease.

[JunesM3]

You may be thinking of preload on the center support bearing, basically just push and hold it foward while tightening the bolts.
I generally mark the postion of it (CSB) before removal.

I see, knew there was something there. Haven’t seen it addressed in any videos. Thank you!

[chris719]

Just in case anyone is curious, I have been using Motul Gear Competition 75W-140 (alien blue stuff) for a year without any issues in my Z4M. I mean, the diff already had issues from previous owners, but I have noticed no noise in tight turns or any worsening of my pinion bearing whine.

[Cubieman]

New to this forum.. at least posting in here but is there any specific way to install the driveshaft back on the car after you replace the pinion seal? Pre-loading it or something?

You may be thinking of preload on the center support bearing, basically just push and hold it foward while tightening the bolts.
I generally mark the postion of it (CSB) before removal.

[JunesM3]

New to this forum.. at least posting in here but is there any specific way to install the driveshaft back on the car after you replace the pinion seal? Pre-loading it or something?

[///Marecki]

Excellent thread - wealth of knowledge. Thank you all.

[George Hill]

It’s 32mm. You can use an impact socket.

Yes, 32mm

[bigjae46]

It’s been awhile. Probably a 32mm. I’ll have to check.


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It’s 32mm. You can use an impact socket.


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[bigjae46]

Can't be. 36mm is way bigger than the lock plate for the nut. Its has to be 30 or 32mm

It’s been awhile. Probably a 32mm. I’ll have to check.


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[TexaZ3]

Replacing the pinion seal in the car and you will lose essentially 0 fluid, basically what is just splashed into the recess of the seal.

Replacing the output shaft seals in the car and again the fluid loss will be very minimal.

Removing the diff and standing on the pinion you can change the diff cover without draining the fluid.

Thanks George.

... why would you not have purchased the fluid from FCP previously?

Because Amazon has it for less than half the price of FCP, and I also have integrity not to return used fluids.

I'm think it's a 36mm and a regular impact socket works.

Can't be. 36mm is way bigger than the lock plate for the nut. Its has to be 30 or 32mm

[George Hill]

For the last option, can you get the paper gasket off without dropping any parts or debris in the fluid?

Yes, the paper gasket usually isn't stuck to the housing very securely. I use a razor blade and angle so it "pushes" the gasket towards the outside of the case. Also keep in mind getting debris in the housing is just as likely whether there is fluid in it or not.

Generally though I do all the work on the diff, run it to temp/extended period without a load (like on the the lift) and then change the fluid.

[bigjae46]

For the last option, can you get the paper gasket off without dropping any parts or debris in the fluid?

Will be tricky. I’d just replace the fluid.


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[Slideways]

Replacing the pinion seal in the car and you will lose essentially 0 fluid, basically what is just splashed into the recess of the seal.

Replacing the output shaft seals in the car and again the fluid loss will be very minimal.

Removing the diff and standing on the pinion you can change the diff cover without draining the fluid.

For the last option, can you get the paper gasket off without dropping any parts or debris in the fluid?

[bigjae46]

Quick question - pinion nut size - 30 or 32mm? And do I need thin wall socket, or regular would fit?

I'm think it's a 36mm and a regular impact socket works.

[Obioban]

... why would you not have purchased the fluid from FCP previously?