Diff leaking - What to do?

Hi!
I'd like you guys to watch the video at the link below. It shows that my differential is oil-wet outside, and now I have to figure out what to do.

The car is 44,000 miles, MY 2008, M3 E92.

It's been doing some vibration under deceleration for a while, but it is intermitent.

Last rain, I tried to "burn out" after a road bumper, 1st gear, wet ground, and it shook too much, I was kinda scared, but no problems after.

So, I suspected there's a problem at the shaft, and now this leak appears.

Let me know your opinions and directions, please.

Thanks in advance.

https://photos.google.com/share/AF1QipOmHS_hlp8JdJCF-ziFqLIHByc6m0uWkeI9E-aOc7bE533hmEEqokhRHvbOVtBmFw/photo/AF1QipPJRoWygt3IDrI9SWul6MovBB0XpbfAWj1iB18?key=MUJRdVF2UWZiMGV3TVMxYUtvYWdwU0dhR2hZUVZ3

I think there is a TIS on how to remove the diff input that includes info on replacing the seal. It’s been a while since I read it, though.

pbonsalb wrote

I think there is a TIS on how to remove the diff input that includes info on replacing the seal. It’s been a while since I read it, though.

For you, it seems obvious that the leak is on the seal, right?

The other leak places are the outputs and those both looked dry. Plus the oil film started at the front, below the input.

Pinion seal leak is common. Replace the seals.

About the shaking thing I said, you think there's a probability that my giubo flex or something will show fatigue when I disassemble it to replace the seal, and I'll have to look for it with urgency?

Is there something I can do to anticipate the surprise, without wasting money with parts that don't need to be replaced?

jvictormp wrote

Is there something I can do to anticipate the surprise, without wasting money with parts that don't need to be replaced?

Your car is 12 years old now, no money spent on parts would be wasted. Regardless of mileage, any soft parts would benefit from being replaced. Guibo, center support bearing, seals, etc. I would use the opportunity to refresh the driveline.

I am using the original flex disk on my 08 6MT car at 101k. I had it off a few years ago at around 80k when I installed a 1 piece driveshaft and it looked too good to replace. I doubt it’s shot at 44k. The driveshaft is probably fine too at that mileage. I’d be focusing on engine mounts. Trans mounts will be fine.

Diy:

https://www.m3post.com/forums/showthread.php?t=1469414

Please, can anybody tell me if I'll be able to inspect the gears when I remove the input seal?

If not, what would be a way to know if the gears had damage due to oil starvation?

I'm asking because I'm not changing the output seals, so there will be no way to inspect the gears by there.

No, you won’t see much. Remove diff, pull rear cover and maybe drivers side output flange and seal if you feel you need to inspect. This shows mostly domestic diffs for non independent rears but you will get the idea of how it all fits together. There is a TIS on the input seal you should read because if you over torque the driveshaft flange you can ruin your diff.

https://www.google.com/search?q=rear+differential+cutaway&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari

I'd like not to inspect

What if I drain the oil and there is no metal signs in it? You think I should inspect?

How much oil did it take to top off the diff? Unless you have been tracking the car or racing through mountains or canyons on a half empty diff or are hearing problems in the diff, I would just reseal your 44k mile diff. Besides even if you look, you may not notice anything if the problem is in the pinion and output bearings.

https://www.newtis.info/tisv2/a/en/e92-m3-cou/repair-manuals/33-rear-axle-rear-wheel-drive-guide/33-11-transmission-housing-with-lid/PeahQlD

The outputs are well covered by the DIY someone linked. The input is where you can do damage when retightening. Use a magnetic drain plug.

Your burnout shaking is almost certainly not internal problems in the diff but rather wheel hop. Always back off when you get wheel hop. That movement can break stuff — probably not in the diff but maybe axles or the diff mounting.

But without taking your car to an expert in these cars, you can’t be sure.

pbonsalb wrote

How much oil did it take to top off the diff? Unless you have been tracking the car or racing through mountains or canyons on a half empty diff or are hearing problems in the diff, I would just reseal your 44k mile diff. Besides even if you look, you may not notice anything if the problem is in the pinion and output bearings.

https://www.newtis.info/tisv2/a/en/e92-m3-cou/repair-manuals/33-rear-axle-rear-wheel-drive-guide/33-11-transmission-housing-with-lid/PeahQlD

The outputs are well covered by the DIY someone linked. The input is where you can do damage when retightening. Use a magnetic drain plug.

Your burnout shaking is almost certainly not internal problems in the diff but rather wheel hop. Always back off when you get wheel hop. That movement can break stuff — probably not in the diff but maybe axles or the diff mounting.

But without taking your car to an expert in these cars, you can’t be sure.

I did not top off. Since I opened the thread, the car's been parked, and I will replace the input seal before riding again, because it's just arrived.

But I'll tell you how much oil will be drained.

About the TIS, I'm definitely following it.

Thanks a lot for your opinion. I don't hear any noise from the diff, and didn't "track" it. =)

Like someone on above says: Pinion seal leak is common. Replace the seals.

I replaced it twice in 6 years time. Not much to concern. The diff only hold 1.1 to 1.2L of diff fluids, fix it as soon as you can.

Hi guys.

I just changed my rod bearings at home, it was a massive time job for me, and so I didn't have enough time to go to the pinion seal. Only checked the fluid level, and would like to know if I'm right.

The car was practically leveled (by eye sight), and when I removed the upper plug, the fluid came out. I put the plug again before I lost too much fluid, but I could see that there was enough fluid. It seemed greenish, almost yellowed.

So I felt less worried. I'm planning on doing the seal next month, but for now I think that I don't need even to refill it.

jvictormp wrote

Hi guys.

I just changed my rod bearings at home, it was a massive time job for me, and so I didn't have enough time to go to the pinion seal. Only checked the fluid level, and would like to know if I'm right.

The car was practically leveled (by eye sight), and when I removed the upper plug, the fluid came out. I put the plug again before I lost too much fluid, but I could see that there was enough fluid. It seemed greenish, almost yellowed.

So I felt less worried. I'm planning on doing the seal next month, but for now I think that I don't need even to refill it.

After the bearing job, the pinion seal swap shouldn’t take you much time at all. I replaced the seal while waiting for oil pick up tube bolts. Get a seal puller and a Miller Pinion Seal Installer 8891 (Bought one for $10 on eBay). Mark the flange nut and a new pinion nut retainer.

Pinion seal DIY:

https://www.m3post.com/forums/showthread.php?t=1469414

I didn't know how much time it would take for me to take off the exhaust, since I never did that before, and put it on after. And was coming the time to go offshore to work (where I am at this right moment), and I needed to run the car so that I could leave it home with my mind in peace, that the rod bearings job was successful

Nice pictures, Bubbles, thanks.

Thanks for reminding me of the DIY, pbonsalb, along with M43S7RO who posted it before.