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E36 M3 (1992-1999) {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999


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Old Sat, Feb-11-2017, 10:21:35 PM   #1
thirtysixnick
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Angry Leaking Rear Differential That Pops/Grinds/Cracks????

Sorry for the lengthiness of this, TLDR below if you're lazy

OKAY SO the story starts a couple of days ago when I decided I haven't "romped" on my car (1997 M3/4/5) in a while so after making half my commute home from school I took some backroads the rest of the way home and decided to take a decently wide (but sharp) long turn while in second gear pretty hard, the rear end kicked out, and made a really bad shuddering sound. I thought maybe it was either the differential or just my car sliding at a faster speed than I was used to and that's just how it sounds because 90's four door packed with plenty of plastic.
I pulled off to the side of the road with the car on, to see if anything smelled, was leaking, or sounded weird, everything checked out and it drove fine for the next TWO days with no "drifting" or aggressive driving.
After backing my car out of the garage to clean it today I decided to take it out to enjoy the cleanliness, yanno?
After taking my first right turn out of my neighborhood it made the same shuddering popping grinding cracking noise I heard when I kicked the ass end out a few days before...
I drove it a little further and over time I realized the noise/feeling was getting worse with just driving straight.
I drove it home as gentle as I could and it continually made the god awful noise while in gear.
The only time I could mask the noise was when I took it out of gear and neutral coasted.
After leaving my car parked for a little in the garage (which looks like where it'll be staying for a little) after my journey it started to leak pretty moderately from the differential.

SO my question is do any of you guys have any clue as to what or why it just randomly started to do this???
It does seem to show signs of the typical differential bushing failure. It's very torque'y in first and second and seems to "surge, especially when cold. So I'm curious if it could be that???

Pictures will be attached below to give you guys an idea of where it's leaking.

Hats off to everyone who just read that book. I appreciate your time.

TLDR: My 1997 M3 sedan's rear differential is making a strange popping/cracking/grinding noise. It started with it just being right turns then turned into making the noises while driving straight. The problem has escalated from a noise to a leak.

Okay for the pictures I can't seem to make them the proper size so I'm just going to link the imgur link for you guys to click yourself.

Images:
http://imgur.com/a/aVUaY

Last edited by thirtysixnick; Sat, Feb-11-2017 at 10:24:11 PM. Reason: didn't include *REAR* differential in title
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Old Sun, Feb-12-2017, 01:33:52 PM   #2
the-git
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Default Re: Leaking Rear Differential That Pops/Grinds/Cracks????

Drain the Diff then pull the end cap.
You may find some loose fasteners.
If it looks good in there, check the torque of the fasteners that secure the ring gear to the diff unit.
It is possible that the diff is failing.
If the torque is good, the CV joints and drive shaft joints need to be inspected.


m
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Old Sun, Feb-12-2017, 06:32:01 PM   #3
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Default Re: Leaking Rear Differential That Pops/Grinds/Cracks????

Quote:
Originally Posted by the-git View Post
Drain the Diff then pull the end cap.
You may find some loose fasteners.
If it looks good in there, check the torque of the fasteners that secure the ring gear to the diff unit.
It is possible that the diff is failing.
If the torque is good, the CV joints and drive shaft joints need to be inspected.


m
Alright thank you!
I plan to get the car up on jacks today to hopefully get a real good look at it.
I'll definitely go through these steps.
Pray it isn't failing...
It hasn't really shown any signs of failing before this last week so I'm just gonna do my best to convince myself it's not that.
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Old Sun, Feb-12-2017, 06:35:21 PM   #4
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Default Re: Leaking Rear Differential That Pops/Grinds/Cracks????

^what he said.

The Allen bolts have been known to back out. Drain the fluid into a clean container and run magnet through it to see if you pick anything up. Pull the cover off to have a look. Check the speed sensor for any large pieces of metal stuck to it, and have a look at all the fasteners inside to make sure they're there.

Though, honestly, if you see anything questionable, I'd just replace the diff. They're cheap enough used and it takes an hour to do.
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Old Sun, Feb-12-2017, 06:36:42 PM   #5
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Default Re: Leaking Rear Differential That Pops/Grinds/Cracks????

Quote:
Originally Posted by thirtysixnick View Post
The only time I could mask the noise was when I took it out of gear and neutral coasted.
And you should elaborate more on this...it's important. Does the noise under happen under load from accelerating? Does it stop when you're in neutral, or stop when you're off the gas?
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Old Sun, Feb-12-2017, 06:46:46 PM   #6
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Default Re: Leaking Rear Differential That Pops/Grinds/Cracks????

Quote:
Originally Posted by fiveightandten View Post
^what he said.

The Allen bolts have been known to back out. Drain the fluid into a clean container and run magnet through it to see if you pick anything up. Pull the cover off to have a look. Check the speed sensor for any large pieces of metal stuck to it, and have a look at all the fasteners inside to make sure they're there.

Though, honestly, if you see anything questionable, I'd just replace the diff. They're cheap enough used and it takes an hour to do.
I'll check this for sure. In the case that the diff has failed, where's the best place to find one? Just asking because to me eBay or classifieds is the only place I'd look besides a junk yard.

Quote:
Originally Posted by fiveightandten View Post
And you should elaborate more on this...it's important. Does the noise under happen under load from accelerating? Does it stop when you're in neutral, or stop when you're off the gas?
The noise happens when under load and in gear. If I put it in neutral and give it no gas it rolls fine. When in gear yesterday it would make a cracking/plastic breaking type of noise and when it (seldom) wasn't doing that it seemed like there was some sort of just thumping noise coming from the back that was quite noticeable even with the windows up.
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Old Sun, Feb-12-2017, 10:51:33 PM   #7
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Default Re: Leaking Rear Differential That Pops/Grinds/Cracks????

Better look at the leak itself:

The leak stopped pretty quickly after I parked yesterday, the drip that is in the picture I posted yesterday hasn't gotten any worse so that's a ______ thing?

These pictures don't show much, but it's only leaked from the left side. (drivers side)
Pictures link:
http://imgur.com/a/7BGX4

on the opposite side it look nothing like this so it's definitely something on the left side.
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Old Mon, Feb-13-2017, 12:15:36 AM   #8
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Default Re: Leaking Rear Differential That Pops/Grinds/Cracks????

Quote:
Originally Posted by thirtysixnick View Post
I'll check this for sure. In the case that the diff has failed, where's the best place to find one? Just asking because to me eBay or classifieds is the only place I'd look besides a junk yard.

The noise happens when under load and in gear. If I put it in neutral and give it no gas it rolls fine. When in gear yesterday it would make a cracking/plastic breaking type of noise and when it (seldom) wasn't doing that it seemed like there was some sort of just thumping noise coming from the back that was quite noticeable even with the windows up.
Your best bet these days (outside of junk yards) is to ask around on Facebook groups. Out here we have "East coast BMW classifieds". I'm sure there is a local group for your area. The diff is heavy, they're expensive on eBay and expense to ship. Check www.car-part.com for junk yard parts in your area.

Quote:
Originally Posted by thirtysixnick View Post
Better look at the leak itself:

The leak stopped pretty quickly after I parked yesterday, the drip that is in the picture I posted yesterday hasn't gotten any worse so that's a ______ thing?

These pictures don't show much, but it's only leaked from the left side. (drivers side)
Pictures link:
http://imgur.com/a/7BGX4

on the opposite side it look nothing like this so it's definitely something on the left side.
That leak isn't really your main concern. It's too high in the casing to deplete the fluid completely. If it's a consequence of an internal problem in the diff, the diff is junk anyways (piece of metal inside that damaged the seal).

You really need to pull the cover off and have a look. Outside of that, we're just throwing guesses out at you. I'd also check the diff bolt to make sure that's not broken.

Here's what I would do:
-Put the rear end in the air and get under the car.

-Check the front diff bolt to make sure it's not broken or bent.

-Have a friend spin one of the wheels and listen for where the noise is coming from (if you hear it at all). You want to make sure it's not the drive shaft u joint (or CV joint for an early DS) or either of the axles. You can put your ear up against things and put your hand on parts to track down any noise you hear. Also, a mechanic's stethoscope is like $5 and very very helpful with stuff like this. The driveshaft is hollow and sound reverberates down it like crazy. I've heard diff problems sound like they're coming from the transmission.

-Drain the diff fluid into a clean container. You will need a stubby 14mm hex bit to do this. The easiest way is to buy one that's supposed to go on a ratchet, and use a 14mm wrench to spin it. The spare tire well is in the way to get a ratchet on it. You want to know how much was in the diff, and you want to know if there was any metal in it. You can drain it through a coffee filter, and/or run a magnet through it to check for metal. The diff speed sensor is also magnetic. It will likely have some metal shavings on it, but see if it's excessive, or any large pieces are stuck to it.

-Pull the diff cover off and have a look inside. You can do this with the diff in the car. Just pull the rear mounting bolts. I'd highly recommend either pulling the front mounting bolt as well, or putting a shim under the diff so it doesn't fall down onto the subframe when you pull the rear bolts.

-Have a look inside with the cover off. Like we said above, the allen head bolts have been known to come loose and back off completely. People have found them in the bottom of the diff, shredded to pieces. Fish around the botton with a small magnetic wand and see if you pull anything out. Spin a wheel so you can examine all of the gearing as it spins. Look for any gouged metal, missing bolts, or metal shavings.

-Find the breather valve on the top of the diff. It's a little rubber thing about the size of your pinky finger, and it's on the backside of the casing, near the passenger side. Pull that off, clean it with some soap and water, or brake cleaner, and put it back on.

-If you don't find anything wrong, fill the diff with new fluid and try again. Use 75W90 with a limited slip additive in it. That's VERY important. It has to be for limited slip diffs. Get yourself some extra limited slip additive as well. It comes in tubes. Our diffs are finicky with LSD additive, i've found that my BMW diffs can be noisy with some LSD gear oils if I don't add a little extra LSD friction modifier. I usually add half a tube in with the LSD gear oil. That's given me good results.


Then try again. Report back with what you find from looking at the diff and we can go from there. This may be something as simple as low fluid, the wrong fluid, or a broken diff bolt. But if you have broken fasteners inside the diff, you need to know about it. It will probably take you an hour or 2 to pull the cover off if you've never done it. It's time well spent.

Don't forget to get 2 new crush washers at the parts store for the drain and fill plugs on the diff. Pull one off and bring it to the parts store so they can match it. Alternatively, you can go to the dealer and get them. I think they're using rubber o rings now for that application.
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Old Mon, Feb-13-2017, 04:42:16 AM   #9
thirtysixnick
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Default Re: Leaking Rear Differential That Pops/Grinds/Cracks????

Quote:
Originally Posted by fiveightandten View Post
Your best bet these days (outside of junk yards) is to ask around on Facebook groups. Out here we have "East coast BMW classifieds". I'm sure there is a local group for your area. The diff is heavy, they're expensive on eBay and expense to ship. Check www.car-part.com for junk yard parts in your area.


That leak isn't really your main concern. It's too high in the casing to deplete the fluid completely. If it's a consequence of an internal problem in the diff, the diff is junk anyways (piece of metal inside that damaged the seal).

You really need to pull the cover off and have a look. Outside of that, we're just throwing guesses out at you. I'd also check the diff bolt to make sure that's not broken.

Here's what I would do:
-Put the rear end in the air and get under the car.

-Check the front diff bolt to make sure it's not broken or bent.

-Have a friend spin one of the wheels and listen for where the noise is coming from (if you hear it at all). You want to make sure it's not the drive shaft u joint (or CV joint for an early DS) or either of the axles. You can put your ear up against things and put your hand on parts to track down any noise you hear. Also, a mechanic's stethoscope is like $5 and very very helpful with stuff like this. The driveshaft is hollow and sound reverberates down it like crazy. I've heard diff problems sound like they're coming from the transmission.

-Drain the diff fluid into a clean container. You will need a stubby 14mm hex bit to do this. The easiest way is to buy one that's supposed to go on a ratchet, and use a 14mm wrench to spin it. The spare tire well is in the way to get a ratchet on it. You want to know how much was in the diff, and you want to know if there was any metal in it. You can drain it through a coffee filter, and/or run a magnet through it to check for metal. The diff speed sensor is also magnetic. It will likely have some metal shavings on it, but see if it's excessive, or any large pieces are stuck to it.

-Pull the diff cover off and have a look inside. You can do this with the diff in the car. Just pull the rear mounting bolts. I'd highly recommend either pulling the front mounting bolt as well, or putting a shim under the diff so it doesn't fall down onto the subframe when you pull the rear bolts.

-Have a look inside with the cover off. Like we said above, the allen head bolts have been known to come loose and back off completely. People have found them in the bottom of the diff, shredded to pieces. Fish around the botton with a small magnetic wand and see if you pull anything out. Spin a wheel so you can examine all of the gearing as it spins. Look for any gouged metal, missing bolts, or metal shavings.

-Find the breather valve on the top of the diff. It's a little rubber thing about the size of your pinky finger, and it's on the backside of the casing, near the passenger side. Pull that off, clean it with some soap and water, or brake cleaner, and put it back on.

-If you don't find anything wrong, fill the diff with new fluid and try again. Use 75W90 with a limited slip additive in it. That's VERY important. It has to be for limited slip diffs. Get yourself some extra limited slip additive as well. It comes in tubes. Our diffs are finicky with LSD additive, i've found that my BMW diffs can be noisy with some LSD gear oils if I don't add a little extra LSD friction modifier. I usually add half a tube in with the LSD gear oil. That's given me good results.


Then try again. Report back with what you find from looking at the diff and we can go from there. This may be something as simple as low fluid, the wrong fluid, or a broken diff bolt. But if you have broken fasteners inside the diff, you need to know about it. It will probably take you an hour or 2 to pull the cover off if you've never done it. It's time well spent.

Don't forget to get 2 new crush washers at the parts store for the drain and fill plugs on the diff. Pull one off and bring it to the parts store so they can match it. Alternatively, you can go to the dealer and get them. I think they're using rubber o rings now for that application.
Thank you SO much all this information, I couldn't be more appreciative.
I'll definitely get back to this later in the week with an update.
Sorry for all the noob'ish remarks and such.
I'm totally new to EVERYTHING pretty much, so wrenching on this car is all a first, but it's a great car to learn on and I know that.

Almost looking forward to toying around under it LOL
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Old Mon, Feb-13-2017, 03:18:55 PM   #10
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Default Re: Leaking Rear Differential That Pops/Grinds/Cracks????

I had this happen to me, but my diff was in fact toast & ended up breaking a block away from my house. Good thing I had a spare one.

I also had my bolt break off, got lucky with that.
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Discussing Leaking Rear Differential That Pops/Grinds/Cracks???? in the E36 M3 (1992-1999) Forum - {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999 at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)