[DreamTime]

Originally Posted by pbonsalb

I never had any noise, but when I changed my fluids around 60k when I did the rod bearings, I used the FM fluid and continue to have no noise. Sometimes I wonder whether lockup might be improved with non FM fluid. I can light up the rear tires pretty easily and have been running 285/35/18 PSS and now 295/30/18 EC Sport. I have all the bolt on mods and tune and probably make close to 400 rwhp, about 15% over stock.

Your car sounds awesome Do you track it? ... Yeah, some people tell me that lockup is potentially decreased with the FM fluid, which would be more of a concern for racing/tracking your car instead of just normal driving conditions. But, the majority of "experts" (certified BMW mechanics mostly) I have asked say that diff performance with FM fluid is not impacted to the point that it necessarily matters..? And, I told all of them that I will be taking my car to the track about once a month. You know, you ask 3 "experts" one question and you get three different answers lol.

I changed out my diff fluid yesterday while my car was on a lift for an exhaust mod, and one benefit of doing that was that we were able to observe the fluid as it came out. It definitely had a pronounced silvery hue to it, so there are metal bits in it, which does not make me super happy! And it was changed not too long ago- 15,000 miles. I put the FM booster fluid in and I have noticed a reduction in clunking noises from my diff, but they have not gone away completely. I am just going to keep paying attention to it.

[DGN23]

Originally Posted by DreamTime

I have about 87000. I have had the car for about a month and a half and I have noticed it the whole time. But, a good friend of mine with an almost identical car, 2008 E92, with almost the same miles has never had this problem or heard any noise from his differential. ? I honestly am not 100% sure what causes it, although I did see a few different theories on other forums. What year is your car? How many miles?

I did speak at length with a certified BMW mechanic about this, and he said it is something he sees all the time. When the differential makes this noise he always switches out the diff fluid with the BMW FM Booster fluid. I am actually doing this today

Only have 30k miles. Drove quite a bit yesterday. And again I didn't hear the noise at all. I'll just monitor for now.

[pbonsalb]

Originally Posted by DreamTime

Your car sounds awesome Do you track it? ... Yeah, some people tell me that lockup is potentially decreased with the FM fluid, which would be more of a concern for racing/tracking your car instead of just normal driving conditions. But, the majority of "experts" (certified BMW mechanics mostly) I have asked say that diff performance with FM fluid is not impacted to the point that it necessarily matters..? And, I told all of them that I will be taking my car to the track about once a month. You know, you ask 3 "experts" one question and you get three different answers lol.

I changed out my diff fluid yesterday while my car was on a lift for an exhaust mod, and one benefit of doing that was that we were able to observe the fluid as it came out. It definitely had a pronounced silvery hue to it, so there are metal bits in it, which does not make me super happy! And it was changed not too long ago- 15,000 miles. I put the FM booster fluid in and I have noticed a reduction in clunking noises from my diff, but they have not gone away completely. I am just going to keep paying attention to it.

I don't track. I did do a local BMWCCA event about 6 years ago. I don't have the time and money for the commitment to track now, but maybe in a couple of years. I mod for fun, but the basic mods I have done would probably work well for a street car that occasionally goes to the track -- braided brake lines and aftermarket pads, Bilstein B8 with H&R springs, 18x9.5/10.5 ARC8 wheels with 265/35 and 295/30 tires, track pipe, intake, tune, pulley, water/meth injection, and I am about to do stiffer subframe and diff mounts.

[DreamTime]

Originally Posted by pbonsalb

I don't track. I did do a local BMWCCA event about 6 years ago. I don't have the time and money for the commitment to track now, but maybe in a couple of years. I mod for fun, but the basic mods I have done would probably work well for a street car that occasionally goes to the track -- braided brake lines and aftermarket pads, Bilstein B8 with H&R springs, 18x9.5/10.5 ARC8 wheels with 265/35 and 295/30 tires, track pipe, intake, tune, pulley, water/meth injection, and I am about to do stiffer subframe and diff mounts.

I apologize for the late response... I started an awesome new job and have been working around the clock. I have only had my car for about 2 months but I want to start putting some money into it. It is my daily driver that will be doubling as a track car until I am committed enough to going to the track that I can justify buying another car. After I get a feel for what my E90 can do stock (well mostly stock, just basic OEM exhaust mod) I want to work on my suspension and upgrade my brakes. In the meantime I have been looking at wheels This seems like a great list of mods you have done, thanks for sharing!! I will likely have questions for you once I start doing more work to my car in a couple months