Pinion seal replacement + diff fluid question

[mtpktz]

I think BMW fluid is Castrol SAF-XJ + FM, so safe to say that's probably is the way to go. Amazon has SAF-XJ on sale right now for $25 per liter.

Thanks for the heads up. Which FM do you use?

[TexaZ3]

Thanks for the heads up. Which FM do you use?

https://www.amazon.com/Ford-XL-3-Fri...3912613&sr=8-4

You need to mix 4.6% which makes it about 48 ml per liter. (1048*4.6% = 48)

[mtpktz]

https://www.amazon.com/Ford-XL-3-Fri...3912613&sr=8-4

You need to mix 4.6% which makes it about 48 ml per liter. (1048*4.6% = 48)

Thanks Alex!

[TexaZ3]

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

[Cronenberged]

About to replace pinion seal on my diff, and having not done it before - do I need to drain the fluid in order to change it? I just did the fluid change like, 1000 miles ago, so would hate to discard perfectly good fluid.

If I do - is the Castrol 75W-140 SAF-XJ + FM still the way to go? Or is there something better out there (aside from super overpriced OE fluid)? Thanks!

I put Amsoil 75w-140 in my diff. I don't have any whining noise but they also have a diff additive if you want to add that. Also the rear of my car is naked and I haven't heard any noise since switching.

[George Hill]

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.

[Obioban]

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

[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.

[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]

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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[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.

[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

[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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[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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[George Hill]

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

Yes, 32mm