Diff Noise and Diff/Trans Leaks

[delirium330]

Frustrating visit to my local indy today! Wanted to get some feedback here before I figure out next steps.

Symptoms: Getting a metal clunk/knock upon torque changes, usually in 1st gear or reverse. Based on a video posted here, was sure that it was the drive shaft u-joint, but we went on a test drive, then they got it up on the lift and looked at the entire drivetrain. Trans guibo, u-joint, etc. all were good to go. They located the sound coming from the differential. While down there they documented leaks in the transmission and differential (see pictures below of the transmission cover/shield and diff.

Background: 89k miles on the odo and I just did a drain and fill of both the transmission and diff (OEM fluids) at 81k miles. I only put on about 3k miles per year. Prior to the 81k mile service, I was changing those fluids every 30k miles or every 3 years, whichever came first.

Question is... what now? Just refill each and let them do the slow seeping leak thing? Looks like there are diff rebuild kits out there? Have no idea what a transmission service would look like for a leak like this... I'm sure the indy shop will have some recommendations, but I'd like to be prepared for that conversation when I call them back. I can DIY a lot, but don't have a lift at home (otherwise most complex work I've done is suspension components, throttle actuators, fluids, plugs, brakes, etc.).

[jhu321]

lol I just did these two things on my new to me 67k mile 2008.

You have a diff seal leak parts costs you 30 bucks from fcp euro. Maybe another 100 in 1 bolts if you want to replace the bolts per bmw instructions.

Your trans is leaking at the shift selector seal. Thats 25 bucks in parts if you go bmw original. Oe is like 5 bucks


The rest of the cost while you’re at it is gonna be your center support bearing which’ll be like 100 bucks.

Prob the most expensive thing will be the shifter rebuild. Since fluid leaded all over the shift selector joint you’re gonna want to replace all the bushings and while you’re at it replace the other stuff which’ll be like 250. Fcp sells a kit.

Net net it’s super cheap for a m3 as far as fixes go. Unfortunately. You’ll prob spend 5-8 hrs of labor if you can’t do it yourself.

I spent a hr to drop the exhaust and drive shaft.

2 hours to do the input seal and 1 axel output seal

2 hrs to do the shift selector seal (it was an absolute bitch to get out).

1 hr to do the center support bearing.

1 hr to rebuild my shifter

And 1 hr to everything back together

Net net 8-10 hrs.

If you’re in the Chicago area. I can prob help you out for a case of beer. lol

[jhu321]

Oh. And the clunk is the infamous cowbell. That’s from your csb flexing too much cuz the rubber has worn thin. YouTube a video called getting rid of the cowbells. They talk about it

[Helmsman]

Originally Posted by jhu321

lol I just did these two things on my new to me 67k mile 2008.

You have a diff seal leak parts costs you 30 bucks from fcp euro. Maybe another 100 in 1 bolts if you want to replace the bolts per bmw instructions.

Your trans is leaking at the shift selector seal. Thats 25 bucks in parts if you go bmw original. Oe is like 5 bucks


The rest of the cost while you’re at it is gonna be your center support bearing which’ll be like 100 bucks.

Prob the most expensive thing will be the shifter rebuild. Since fluid leaded all over the shift selector joint you’re gonna want to replace all the bushings and while you’re at it replace the other stuff which’ll be like 250. Fcp sells a kit.

Net net it’s super cheap for a m3 as far as fixes go. Unfortunately. You’ll prob spend 5-8 hrs of labor if you can’t do it yourself.

I spent a hr to drop the exhaust and drive shaft.

2 hours to do the input seal and 1 axel output seal

2 hrs to do the shift selector seal (it was an absolute bitch to get out).

1 hr to do the center support bearing.

1 hr to rebuild my shifter

And 1 hr to everything back together

Net net 8-10 hrs.

If you’re in the Chicago area. I can prob help you out for a case of beer. lol

I would love a neighbour like this!

[delirium330]

Originally Posted by jhu321

Oh. And the clunk is the infamous cowbell. That’s from your csb flexing too much cuz the rubber has worn thin. YouTube a video called getting rid of the cowbells. They talk about it

Appreciate your comments on the leaks. Regarding the cowbells, I agree that it sounded like various videos I have seen with this sound... many of those threads have tons of responses that look like, "absolute 100% drive shaft". So when I got to the shop and did a test drive, fully expected them to come back after getting it on the lift to verify drive shaft. Was surprised on the report as they said they specifically looked close at the guibo, overall drive shaft and u-joint, etc. and specifically said the sound was coming from the diff.

For what its worth, this shop only works German cars, used to be BMW only. Have only had work done there twice (rod bearings and valve covers, then engine and trans mounts). They have two 25+ year BMW master mechanics. Anyway, a mechanic I haven't seen there before was diagnosing this one, and seemed to know what we was doing. Was knowledgeable about common issues, what to look for, etc. So have trouble not trusting the diagnosis as the diff causing the noise.

[jhu321]

Originally Posted by delirium330

Appreciate your comments on the leaks. Regarding the cowbells, I agree that it sounded like various videos I have seen with this sound... many of those threads have tons of responses that look like, "absolute 100% drive shaft". So when I got to the shop and did a test drive, fully expected them to come back after getting it on the lift to verify drive shaft. Was surprised on the report as they said they specifically looked close at the guibo, overall drive shaft and u-joint, etc. and specifically said the sound was coming from the diff.

For what its worth, this shop only works German cars, used to be BMW only. Have only had work done there twice (rod bearings and valve covers, then engine and trans mounts). They have two 25+ year BMW master mechanics. Anyway, a mechanic I haven't seen there before was diagnosing this one, and seemed to know what we was doing. Was knowledgeable about common issues, what to look for, etc. So have trouble not trusting the diagnosis as the diff causing the noise.

simple... diff have nothing that makes a cow bell sound... to make a cow bell sound. you need something hollow... the diff is gears and tightly packed in with fluid... if its making that clink sound then something is super loose and you would feel it in the drive. the cowbell is a known problem with our cars it can be caused by either the CSB, the GUIBO, or the CV Joint. it makes the sound cuz the drive shaft is hollow hence sounds like a cow bell. it costs you practically nothing to get a CSB done... before you go doing a diff rebuild. do the CSB... the CSB failure is hard to diagnose on visual inspection cuz it'll look perfectly fine on a lift, its only when you try to spin it and put torque on it will it deflect and cause the drive shaft to contort and hit something causing the cow bell sound. if you're gonna do the diff, you should do the CSB anyway cuz you're pulling the driveshaft to get the diff unbolted.. you're paying the labor anyway. Don't go through all that with a diff rebuilt to come back to yea you still have the sound.

I just did mine, i had the sound, after i was done, I don't have the sound anymore. but i did do all 3 (guibo, CSB, and CV) to be safe cuz i really don't want to go back in there again.

[jhu321]

this guy is one of the more reputable bmw shops on youtube and he explains it fully what's causing the cowbell..

[delirium330]

Originally Posted by jhu321

simple... diff have nothing that makes a cow bell sound... to make a cow bell sound. you need something hollow... the diff is gears and tightly packed in with fluid... if its making that clink sound then something is super loose and you would feel it in the drive. the cowbell is a known problem with our cars it can be caused by either the CSB, the GUIBO, or the CV Joint. it makes the sound cuz the drive shaft is hollow hence sounds like a cow bell. it costs you practically nothing to get a CSB done... before you go doing a diff rebuild. do the CSB... the CSB failure is hard to diagnose on visual inspection cuz it'll look perfectly fine on a lift, its only when you try to spin it and put torque on it will it deflect and cause the drive shaft to contort and hit something causing the cow bell sound. if you're gonna do the diff, you should do the CSB anyway cuz you're pulling the driveshaft to get the diff unbolted.. you're paying the labor anyway. Don't go through all that with a diff rebuilt to come back to yea you still have the sound.

I just did mine, i had the sound, after i was done, I don't have the sound anymore. but i did do all 3 (guibo, CSB, and CV) to be safe cuz i really don't want to go back in there again.

Got it, makes sense, and thanks for the detailed explanation. Exactly what I was hoping to discuss prior to calling the indy back. And I'll check out that video.

[jhu321]

also make sure they follow the diff flange balancing measures when they pull your drive shaft... your diff can be marked with a white, yellow or blue mark and depending on the color those would require that you keep track of where the weighted washer or bolt needs to go. the white or no mark is the only one that doesn't require anything special. it is VERY common that alot of shops don't know about this cuz they can go through hundreds of cars and never see a diff that's marked with a need to balance. if you don't follow you could end up with a humming or a vibration in your drive line.