Rear Diff Shaft Seal advice

[PaulS]

Hi everyone,

On my '10 30i (n52) I have a leaking rear differential shaft seal.
This is the seal on the driveshaft side facing forward.

Number 8 in the picture.

Looking at videos and posts it looks like the rear driveshaft can be removed from the center support bearing and slides off the rear diff once the insert nut is loosened. Can anyone confirm this?

I've had a heck of a time finding a service manual for this vehicle. Anyone source a manual similar to Bentley for the e70 X5?

Thanks for any input.

[ChuckG]

Last time I had a pinion shaft seal go bad I had it replaced. Not cheap. Then a few months later the pinion bearing started failing. I believe that the failing pinion bearing took the seal out. Like me you may already need to be rebuilt. This was not on a BMW.

[ard]

Sorry, my experince is on the E39. There is a 'setting of preload' for the input seal that had to be done when I did all 3 seals. Has been fine for the last 30k.

There is no 'service manual'- BMW has gone electronic. Look up Rheingold or BMW Workshop Manuals

GL

[Thecastle]

I know this may not be the solution your looking for..... But it could save you money,.

You could also as a cost save just lower the oil level in the diff and not worry about it. The diffs have a tolerance on how much oil they need and just keep the level below the diff seal and monitor occasionally for more leakage. I know this isn't fixing the problem, but it is a lot cheaper, and their isn't a lot of risk in running the diff dry, since the case seal is not leaking. Just keep an eye on it.

I also have found that different diff fluids more easily leak than others. It might be worth while to try a couple of different diff fluids, BMW's, redline, etc. to see if that stops the leaking.

[ard]

Originally Posted by Thecastle

I know this may not be the solution your looking for..... But it could save you money,.

You could also as a cost save just lower the oil level in the diff and not worry about it. The diffs have a tolerance on how much oil they need and just keep the level below the diff seal and monitor occasionally for more leakage. I know this isn't fixing the problem, but it is a lot cheaper, and their isn't a lot of risk in running the diff dry, since the case seal is not leaking. Just keep an eye on it.

I also have found that different diff fluids more easily leak than others. It might be worth while to try a couple of different diff fluids, BMW's, redline, etc. to see if that stops the leaking.

Wouldnt it eventually get to the point you describe?

Then he can find out if the minimum fill level is a 'theory' or if there really is a need for lubrication to prevent destruction....

[the_ulf]

interesting thought, were it not for the fact that the purpose of the oil is not only to lubricate but also to cool the gearing, which heats up quick due to a lot of friction happening. but by all means, try and report back.

[Thecastle]

Originally Posted by the_ulf

interesting thought, were it not for the fact that the purpose of the oil is not only to lubricate but also to cool the gearing, which heats up quick due to a lot of friction happening. but by all means, try and report back.

Yes, I'd understand your reluctance to run your oil at a lower level to stop the leak instead of replacing the seals which are labor intensive and can be expensive. Replacing the seal is the conservative thing to do if an oil swap doesn't solve the leak.

However, I've actually been doing exactly this. No my diff hasn't blown up or making some awful noise. I have a leaking front differential at the driveshaft seal. It was discovered after I did a front diff service, and I had my indy take a look at it. We opted to lower the diff fluid to near the minimum amount that BMW specifies in their service manuals and it solved my leak inexpensively (don't remember the minimum recommendation). Its been running this way for 5k miles without any obvious issues (no leaks and no change in performance). Diff fluid like all fluids (oil, tranny, etc.) in a car have an acceptable range. My indy has had success with this approach of lowering the fluid level to eliminate leaks, assuming its not leaking at the case seal or the drain bolts.

While diff fluid provides some of the cooling, there is an acceptable range of fluid levels needed to provide sufficient cooling. We already know since he's leaking and I'm at a lower level and we haven't blown our diffs so long as your above BMWs design minimum you'll be fine. Adding dry lubricant like NoS2 could help as well.

Something else to consider, I see diffs for this car going from salvage yards in the $300-350 range for low mileage grade A examples, which means diff replacement isn't horribly expensive if running fluid at a low level leads to "premature" diff failure.



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So why do I gamble a little? 1st this isn't my only car. 2nd I purchased my X5 used its a 2008 4.8i fully loaded and currently has 92K miles and is worth about 10K on trade in. In the few months I've owned it I've spent ~5K in maintenance and repairs (new alternator, new CCV system, all fluids changed/flushed, new rain tray, new spark plugs, air filters, front suspension refresh, new coolant sensor, new maf). Its very easy to spend 50% of the cars worth in repairs/maintenance per year. Which makes you question why even keep an old car if its the same cost in repairs and maintenance as you would pay in depreciation on leasing a new X5. So that's why I do my own work where ever possible and as much preventative maintenance as possible and watch minor issues. I'm not tied up in the fact that this car was over 70K new, I just look at it as whats it worth today, and does it make sense to spend money right away on minor issues when there are plenty of other things that will break and be expensive to fix when the vehicle is currently not worth a whole lot.

[PaulS]

Thanks for the great dialogue. I have been quoted $530 from the dealer and $500 from an Indy BMW specialist.l to replace the seal. It's mostly labour cost since the seal is only $25.

If I can find the special tools to remove the driveshaft and nut I'll do it myself. In the meantime I have replaced the fluid with slightly thicker 75w140 and will see if that helps. I'm not in a position to replace the diff in the event of a failure but there are some choices here.

Great forum everyone!

[bawareca]

Originally Posted by Thecastle

Something else to consider, I see diffs for this car going from salvage yards in the $300-350 range for low mileage grade A examples, which means diff replacement isn't horribly expensive if running fluid at a low level leads to "premature" diff failure.

Well, the REAR diffs would be anywhere from $1000 to $2000, more labor intensive to replace too. E70 rear diffs are known to fail catastrophically without reason or warning, running the fluid low could only worsen the problem. Contrary, the front diffs run with no load 99% of the time, so it should be ok even with half the amount of fluid inside.

[PaulS]

Just an update that I took it to an independent BMW specialty shop (Burnaby BC) to have the seal replaced. They got the job done, but there were no "special" BMW tools used. Evident from the insert nut and flange looking mangled like a pipe wrench was used. Lesson learned, I could have done this myself and save $400. Anyways the job is done now and they do warranty against leaks for 2 years.

Thanks to all who offered feedback.