Rear Differential (pumpkin) leak - do we have DIY on the forum?

[TerminatorX5]

Hello.


It seems that I have developed a leak on the rear "pumpkin"... Last night saw oily stain on the garage floor (sweep floor almost every other day, so the stain is new), and after crawling under the car, saw oily surface on the rear differential. I will wipe it out to see where it is coming from but from the looks of it, seems to be coming from the shaft seal...

Naturally, I have searched the site for the info, and it seems that since I will be doing rear differential, I will need the proper fluid replace the one that is about to get drained... It is recommended on numerous threads to use 75W-90 weight fluid, from Red Line, or BMW... I also know there is fluid in this weight from Lubro Moly - anyone has any opinion on that brand? I use their oil for oil changes, (oil is made in Germany), so was wondering if it makes sense to try them in the diff...

Also, couple more technical questions -

where is the fill plug? found the drain plug, can't see the fill plug

is it wise to replace the rest of the seals even if they look bone-dry? shaft seal, 33107609536. there is also a gasket set, 33101428092 (despite saying ENDED in RealOEM, it is still listed at a dealer's parts counter) - should I get them all and replace them? I kind of subscribe to a theory that if "it ain't broken, don't fix it"...

Is there a DIY or a post/thread that specifies the exact procedure for the shaft seal replacement? the SEARCH and GOOGLE SEARCH did not bring much joy, but again, i am not that good with the search button...

Thanks

[Ricky Bobby]

If you have to drop the diff to replace the seal, I would replace any seal that gets disturbed or exposed upon removing the rear diff.

Fill plug should be at the 3:00 or 9:00 position roughly if the drain plug is at 6:00 on the diff.

I used Redline 75w-90 but if Lubro Moly has a 75w-90 synthetic that you like then by all means use it.

If it were me, I'd also change the fluid on the front diff at the same time and the transfer case with Xdrive fluid just to cover my bases from a maintenance standpoint.

[TerminatorX5]

Thanks Jay, that is a +1 on Lubro Moly ( or, I should say, it is not a -1)

I will try to see if i can find the fill plug at those locations... and will look into the front differential too...

And it makes sense, if dropping the differential, the other seals will get disturbed, so i would need to replace them... on the other hand, if instead of dropping the differential, what if i try to drop the shaft itself?... wonder if this is a possibility...

in the process i will inspect the guibo - what else there that i should be checking out?

[Doru]

Hi Terminator. I had that issue of diff fluid leaking out on one side of the rear differential. My issue was due to the fact that I changed the rear ball joint, and somehow I popped out the half shaft from the differential. What I did was: I just placed it back with a pry bar. Popped back in without a problem. No more leaks in over a year. If this happened to you because you worked on the suspension, just do what I described, but be careful where you chose the levering point(s). If the half shaft is in place, and you are leaking oil, then you need to replace the seal. The seal is not airtight, but the diff oil will never leak, because there is no pressure in the pumpkin, and also the oil level is at the half shaft level as well.

[BigBlack48is]

+1 on Redline 75w-90

I did front / rear fluid changes on mine and spent the $40 for the "magic bottle" of x-drive goop. So I should be good to go until that 200k miles mark

[TerminatorX5]

i did not touch anything in the back of the car - for that matter of fact, the only thing was done is a left outer CV boot, yesterday, AFTER I discovered the leak, and the mechanic guy and myself were under the car looking at the differential... The mechanic does "house calls" and is very reasonable, only $50 for the boot change so he will be looking into the diff repair too...

the leak is happening from the the front part of the diff, where the main shaft is going to, not from the sides, both sides are dry... as Jay said earlier, if I drop the whole thing, then it makes sense replacing the side seals too... if not - then only one seal...

It is also nice to know that the seal is not airtight and that the level is at half shaft... Does it mean that one can not possible overfill the differential, as something at 2 qts that is not supposed to be "full" can not be overfilled with an extra ounce or two fluid?... just checking on the tolerances for the fluid level...

I also read, that to drain all the fluid from the differential, I should drive like a maniac (well, I added the maniac part!!) for about 100 miles and THEN drain hot diff fluid in attempt to rid the chamber of all the fluid - does this still stand correct?

[Ricky Bobby]

When the car is parked on level ground (or in the air sitting level) you fill up the diff until oil comes out of the fill hole, should be 1.9 quarts i believe. Pretty hard to mess up unless the car isn't level, etc.

Yes for the diffs you will want to change them pretty hot, as you can imagine 75w-90 is pretty thick even when warm as opposed to engine 5w-30.

[TerminatorX5]

Originally Posted by Ricky Bobby

When the car is parked on level ground (or in the air sitting level) you fill up the diff until oil comes out of the fill hole, should be 1.9 quarts i believe. Pretty hard to mess up unless the car isn't level, etc.

Yes for the diffs you will want to change them pretty hot, as you can imagine 75w-90 is pretty thick even when warm as opposed to engine 5w-30.

as i did not find the fill hole yet, i did not visualize the process, but it makes sense - if the fill hole is below the top of the chamber, naturally the chamber can not be filled to the top when the car is on a level surface... understood the overfilling part...

next question from the stupid series - if the fluid is so think (of course, at 75w-90!!) and should be hot to be removed from the chamber - does the fresh fluid need to be warmed up before filling? will it flow freely? I suspect that a little hand pump needs to be used to fill the pumpkin?

[TerminatorX5]

Originally Posted by BigBlack48is

+1 on Redline 75w-90

I did front / rear fluid changes on mine and spent the $40 for the "magic bottle" of x-drive goop. So I should be good to go until that 200k miles mark

+1 for Redline

+1 for Liqui Moly...

still counting...

[JCL]

Originally Posted by TerminatorX5

+1 for Redline

+1 for Liqui Moly...

still counting...

Any name brand. It isn't like it is going to make a difference to the life of the differential.

As to temperature, room temperature is fine. If it is cold outside and you are working in an unheated garage, then driving it to warm it up isn't a bad idea, but if it is at normal ambients it will drain fine.

Could we refer to the differential cover as a cover, or ring gear cover, not a pumpkin? The seal on the front where the driveshaft enters is called a pinion seal. The side seals are output shaft seals, or halfshaft seals.

Do you understand the procedure with respect to pinion preload? I presume it is possible to mark the retention nut and return it to exactly the same position to restore the original preload, as with other differentials. You don't usually just torque it up, failure to restore the correct preload is a frequent cause of subsequent failure.

I've never taken a differential out to replace a pinion seal, but I've never done this job on an X5 either. Usual procedure is to disconnect the driveshaft. If there is reasonable access I don't understand the reason to drop the differential.