High Pitch Sound From Diff

[Matthew III]

Originally Posted by STooK

Yup, sounds like we have the exact same issue. I also found it hard to believe that there aren't more people with the same issue out there.

So what are you going to do? Sounds like the only option is to replace the diff or rebuild it. Either way it's gona be costly...

I'm gonna take it to a shop on Monday to get a second opinion. I'm thinking bc it's a whine and not metal groaning, it won't require a full rebuild but the pinion gear replacement. il let you know

also another article about the exact same noise, pointing to the pinion gear. http://fixyourdifferential.weebly.com/

[STooK]

Originally Posted by MattyRice

I'm gonna take it to a shop on Monday to get a second opinion. I'm thinking bc it's a whine and not metal groaning, it won't require a full rebuild but the pinion gear replacement. il let you know

also another article about the exact same noise, pointing to the pinion gear. http://fixyourdifferential.weebly.com/

Good luck man, hopefully you won't have to buy a new rebuilt diff.

Good article, I've seen that 135i video and it sounded just like our diffs. Good luck tomorrow!

[Matthew III]

Originally Posted by STooK

Good luck man, hopefully you won't have to buy a new rebuilt diff.

Good article, I've seen that 135i video and it sounded just like our diffs. Good luck tomorrow!

Yup it's the diff. I put my ears onto a sethoscope while car was going 70 mph on a rack, sounded winded and whiny, but no metal groans. Basically the diff is on the way out, most likely from prior owner mashing the hell out of it. I'm going to buy a rebuilt diff, probably from that website you suggested earlier. No point doing a partial rebuild, cost effective wise. That's $1500 plus another $500 in labor and $200 for oil

Good news is that it still has some life left, about 15K miles or so. At least I know what's causing it. Thanks for the help Stook!

[STooK]

Originally Posted by MattyRice

Yup it's the diff. I put my ears onto a sethoscope while car was going 70 mph on a rack, sounded winded and whiny, but no metal groans. Basically the diff is on the way out, most likely from prior owner mashing the hell out of it. I'm going to buy a rebuilt diff, probably from that website you suggested earlier. No point doing a partial rebuild, cost effective wise. That's $1500 plus another $500 in labor and $200 for oil

Good news is that it still has some life left, about 15K miles or so. At least I know what's causing it. Thanks for the help Stook!

Ah that stinks, but glad you were able to diagnose it! It helped me as well because I wasn't able to confirm if mine was actually the diff.

Yea, you are better off just getting the rebuilt diff. It'll be $1600+ after shipping costs (you have to pay to ship your core back and it's about 100 lbs so $$$$) and then labor and fluids like you said but at least you will be getting a new unit. Even used units are going for ~$1,000 and no guarantee that it won't have issues of its own. For the fluids, I skipped the BMW fluid w/ extra FM and just went for the Castrol Synthrax that's $67 from FCP Euro. Just don't forget to break it in for 1200 miles after and get the fluid replaced again after.

Our cars are pretty robust though so hopefully you won't have any other issues afterwards. This was also my first big repair for the car (besides rod bearings) and they are right, German cars are expensive to maintain. But it's worth it so far!

[Matthew III]

Originally Posted by STooK

Ah that stinks, but glad you were able to diagnose it! It helped me as well because I wasn't able to confirm if mine was actually the diff.

Yea, you are better off just getting the rebuilt diff. It'll be $1600+ after shipping costs (you have to pay to ship your core back and it's about 100 lbs so $$$$) and then labor and fluids like you said but at least you will be getting a new unit. Even used units are going for ~$1,000 and no guarantee that it won't have issues of its own. For the fluids, I skipped the BMW fluid w/ extra FM and just went for the Castrol Synthrax that's $67 from FCP Euro. Just don't forget to break it in for 1200 miles after and get the fluid replaced again after.

Our cars are pretty robust though so hopefully you won't have any other issues afterwards. This was also my first big repair for the car (besides rod bearings) and they are right, German cars are expensive to maintain. But it's worth it so far!

Dam I had a feeling they wouldnt help pay for the core shipping back lol. Dude what kills me is the 1200 mile break in. I save this car for special roads and covered 1,000 miles in the last 6 months. Yea I bought the BMW+FM booster for $200, which I'll save it for after the break in. I do NOT want that sound coming back so I'm willing to spend the $ even if it's unecessary. I'll check the castrol for the break in period, thanks.

[STooK]

Originally Posted by MattyRice

Dam I had a feeling they wouldnt help pay for the core shipping back lol. Dude what kills me is the 1200 mile break in. I save this car for special roads and covered 1,000 miles in the last 6 months. Yea I bought the BMW+FM booster for $200, which I'll save it for after the break in. I do NOT want that sound coming back so I'm willing to spend the $ even if it's unecessary. I'll check the castrol for the break in period, thanks.

Yea I feel your pain. I'm 300 miles in and I only drive about 3-4000 miles a year as well. What's worse is I had to do a 1000 mile break in for my rod bearings right before this lol.

Diffsonline didn't have the best communication but they take about a week and half to ship your diff out and you have 2 weeks to send it back. Their product seems to be good though. As for the fluid, either one should be fine. I'm getting some groaning at slow turns when the diff is cold but goes away when warmed up. I heard the FM booster allows more slip to quiet down the diff and I rather have it working the way it was designed to vs sacrificing performance for noise. Plus it's 3x cheaper so I just went with that.

When do you think you will be ordering the new diff? Are you planning on getting any upgrades done?

[Matthew III]

Originally Posted by STooK

Yea I feel your pain. I'm 300 miles in and I only drive about 3-4000 miles a year as well. What's worse is I had to do a 1000 mile break in for my rod bearings right before this lol.

Diffsonline didn't have the best communication but they take about a week and half to ship your diff out and you have 2 weeks to send it back. Their product seems to be good though. As for the fluid, either one should be fine. I'm getting some groaning at slow turns when the diff is cold but goes away when warmed up. I heard the FM booster allows more slip to quiet down the diff and I rather have it working the way it was designed to vs sacrificing performance for noise. Plus it's 3x cheaper so I just went with that.

When do you think you will be ordering the new diff? Are you planning on getting any upgrades done?

Lucky for me the prior owner already did the new RB break in for me

Funny I also emailed diffsonline. Dan was dry in his response but timely. Looks like it includes everything so no need to buy new seals, just oil. I'm actually going to entertain flushing the diff fluid and add in the FM booster. $200 to negate $2500 is worth the risk and I can't live with myself if I dont explore this option first. Plus the car has 65K miles, it doesn't make sense to me that it can go out this fast. If it persists, I'll just keep it as is and fix it next year. I've spent enough on this car in 2020. I like keeping the car stock to hold resale value (and mpg lol).

BTW I re-read our convos, and realized you changed the diff with a rebuilt one and added new bushings? I read that harder bushings will groan while turning.

[ha9981]

There is no RB break-in...

[STooK]

Originally Posted by ha9981

There is no RB break-in...

I've heard both sides of the argument but the shop that did the work (ACM) recommended it and I rather be safe than sorry so I took it easy the first thousand miles.

[Matthew III]

Originally Posted by STooK

Yea I feel your pain. I'm 300 miles in and I only drive about 3-4000 miles a year as well. What's worse is I had to do a 1000 mile break in for my rod bearings right before this lol.

Diffsonline didn't have the best communication but they take about a week and half to ship your diff out and you have 2 weeks to send it back. Their product seems to be good though. As for the fluid, either one should be fine. I'm getting some groaning at slow turns when the diff is cold but goes away when warmed up. I heard the FM booster allows more slip to quiet down the diff and I rather have it working the way it was designed to vs sacrificing performance for noise. Plus it's 3x cheaper so I just went with that.

When do you think you will be ordering the new diff? Are you planning on getting any upgrades done?

I just flushed the diff and put in new with FM. Still makes the noise but slightly lower pitch now. Shop said no metal glitter in the oil which is a good sign. I'm thinking the 08 models are cursed with diffs that dont break in well. Noise still there, maybe after driving for a while it will progressively get quieter who knows. After thinking about it I'm going to leave it as is, not worth the money to replace it.

[STooK]

Originally Posted by MattyRice

I just flushed the diff and put in new with FM. Still makes the noise but slightly lower pitch now. Shop said no metal glitter in the oil which is a good sign. I'm thinking the 08 models are cursed with diffs that dont break in well. Noise still there, maybe after driving for a while it will progressively get quieter who knows. After thinking about it I'm going to leave it as is, not worth the money to replace it.

Yea, I replaced my fluid too and it seemed to have gotten quieter initially but wasn't the case. My mechanic also said the diff looked fine when he removed it from the car so I'm not even sure if it's really an issue. He didn't take it apart though so who knows what it really looks like inside.

I guess just drive on it for now and see if it gets worse.

[ha9981]

Originally Posted by STooK

I've heard both sides of the argument but the shop that did the work (ACM) recommended it and I rather be safe than sorry so I took it easy the first thousand miles.

If you want to be safe then keep it under 3K RPM until you pass it on to the next owner. You are smarter than that.

The bearings make no contact with the journal, it floats on a film of oil. So what would you be breaking in, the oil?

Let's not spread disinformation.

[Matthew III]

Originally Posted by STooK

Yea, I replaced my fluid too and it seemed to have gotten quieter initially but wasn't the case. My mechanic also said the diff looked fine when he removed it from the car so I'm not even sure if it's really an issue. He didn't take it apart though so who knows what it really looks like inside.

I guess just drive on it for now and see if it gets worse.

Dude I've been driving it around more and noticed the noise has decreased tremendously. Seems like the extra miles makes a difference so the gears are properly lubed. I've heard it decreases the performance of the LSD, personally I'm ok with this since I'm not tracking or turning sideways with the car, just fun spirited drives occasionally. What a relief...def recommend the SAF-XJ + FM booster if there's noise you can't tolerate.

Originally Posted by ha9981

If you want to be safe then keep it under 3K RPM until you pass it on to the next owner. You are smarter than that.

The bearings make no contact with the journal, it floats on a film of oil. So what would you be breaking in, the oil?

Let's not spread disinformation.

Hey let's be a little more respectful. Stook isn't spreading misinformation, merely conversing what's been heard. Thanks for the correction though.

[STooK]

Originally Posted by Matthew III

Dude I've been driving it around more and noticed the noise has decreased tremendously. Seems like the extra miles makes a difference so the gears are properly lubed. I've heard it decreases the performance of the LSD, personally I'm ok with this since I'm not tracking or turning sideways with the car, just fun spirited drives occasionally. What a relief...def recommend the SAF-XJ + FM booster if there's noise you can't tolerate.




Hey let's be a little more respectful. Stook isn't spreading misinformation, merely conversing what's been heard. Thanks for the correction though.

Glad it worked out for you and you didn't have to replace a diff for no reason! My diff whine is still sort of bugging me (from poly diff bushings) but I do really enjoy how the car transformed after solid subframe bushing and poly diff bushings. Still have about 600 more miles to go but at least I'm at the half point. I can't wait until it's broken in to see what the car really can do.

And to the other guy, I wasn't spreading misinformation just sharing my experience. You can take it or leave it.