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The BMW E46 ///M3 is the M version E46 and puts out an amazing 333 HP and 262 lb-ft of torque at stock specs! There are an amazing amount of modifications for both the coupe and convertible models so read up and get started modifying your cars today!

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Old 03-04-2016, 09:05 AM   #1
bm_ch
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Differential service DIY

Hello,

I've studied very deeply differentials from E36 and other brands but never done one, before posting. From other posts, it seems feasible on E46M3... changing bearings and resetting preload is within reach but hardcore. DIY jobs are such a pleasure... I've got several difficult to answer questions if enthusiasts could stop by and help


-First seems simple to check the diff relative wear. Well, tech opinions seems to differ a lot ! Some says that E46 M3 is a race car and have a lot of backlash and is not wear... Other source says that one side has more play... and other says that you just need to put new fluid with additives to take the noise go away. Well... how can we be 100% sure that the differential is dead please ?

-My diff is making humming noise on full turns and has > 60k Miles. BMW Tech says it is at its end of life, which is normal. Under normal usage, what are the parts that really wear out ? Only the bearings that mess preloads or must I have to change ring and pinion ?

-Finding shims will be the hardest part. If ring and pinion are OK and I don't upgrade them, maybe reshimming is not necessary (seen examples) ?

-Do you know if the M Variable differential has clutches that need to be changed ? I really tried to find on the web examples. No one seems to have been that deep. Only thing I've learned is that it has a "pump" that presses when speed is different on both sides. Some says that you can just flip clutch plates for a second life on locking clutches.

-When rebuilding the diff we must check the gear pattern with a special paste. It is said that we should remount the diff on the car, apply brake and apply torque on the pinion to check if all is aligned properly. But on videos of other brands, some block it and just apply torque to check pattern. Can we do this also because it is a tedious job to remount the diff... and if yes how to check it properly without mounting it ?

Hope it is clear enough... Any help is welcome.
Please be sure that I will be posting the process here - the least I can do.

Last edited by bm_ch; 03-04-2016 at 09:14 AM.
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Old 03-04-2016, 02:39 PM   #2
E46 WOT
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Quote:
Originally Posted by bm_ch View Post
Hello,

I've studied very deeply differentials from E36 and other brands but never done one, before posting. From other posts, it seems feasible on E46M3... changing bearings and resetting preload is within reach but hardcore. DIY jobs are such a pleasure... I've got several difficult to answer questions if enthusiasts could stop by and help


-First seems simple to check the diff relative wear. Well, tech opinions seems to differ a lot ! Some says that E46 M3 is a race car and have a lot of backlash and is not wear... Other source says that one side has more play... and other says that you just need to put new fluid with additives to take the noise go away. Well... how can we be 100% sure that the differential is dead please ?

-My diff is making humming noise on full turns and has > 60k Miles. BMW Tech says it is at its end of life, which is normal. Under normal usage, what are the parts that really wear out ? Only the bearings that mess preloads or must I have to change ring and pinion ?

-Finding shims will be the hardest part. If ring and pinion are OK and I don't upgrade them, maybe reshimming is not necessary (seen examples) ?

-Do you know if the M Variable differential has clutches that need to be changed ? I really tried to find on the web examples. No one seems to have been that deep. Only thing I've learned is that it has a "pump" that presses when speed is different on both sides. Some says that you can just flip clutch plates for a second life on locking clutches.

-When rebuilding the diff we must check the gear pattern with a special paste. It is said that we should remount the diff on the car, apply brake and apply torque on the pinion to check if all is aligned properly. But on videos of other brands, some block it and just apply torque to check pattern. Can we do this also because it is a tedious job to remount the diff... and if yes how to check it properly without mounting it ?

Hope it is clear enough... Any help is welcome.
Please be sure that I will be posting the process here - the least I can do.
Have you flushed the fluid and put in Redline (I think I used 75W90 Gear Oil) to see if that gets rid of the symptoms first? 60k seems awfully early to have a diff go bad. Changing to that eliminated a lot of noises for me around 120k miles thru the diff.
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Old 03-05-2016, 10:58 AM   #3
Kong Sheng Han
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Your diff is fine. That humming/groan can possibly be fixed with OE fluid, which contains FM booster. Or you could buy OEM and add the friction modifier separately. When I changed my fluid for regular maintenance I used OEM and decided not to use the FM I bought (I actually forgot to add it in), but the groan doesn't bother me.
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Old 03-08-2016, 04:45 AM   #4
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Actually I just did about 10 circles with full left lock then another 10 to the right. Head spinning but noise have been gone for 18 months at least. I run Castrol Syntrax 75W~140W no additives.
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Old 03-09-2016, 12:25 PM   #5
bm_ch
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Originally Posted by Kong Sheng Han View Post
Your diff is fine. That humming/groan can possibly be fixed with OE fluid, which contains FM booster. Or you could buy OEM and add the friction modifier separately. When I changed my fluid for regular maintenance I used OEM and decided not to use the FM I bought (I actually forgot to add it in), but the groan doesn't bother me.
Okay you seem to know well this diff... My mechanic has the same opinion than you. Detailed in my other post :

http://forum.e46fanatics.com/showpos...9&postcount=21
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Old 03-09-2016, 12:51 PM   #6
Kong Sheng Han
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Originally Posted by bm_ch View Post
Okay you seem to know well this diff... My mechanic has the same opinion than you. Detailed in my other post :

http://forum.e46fanatics.com/showpos...9&postcount=21
Yes, that's the diff fluid I used. I went with the Ford Racing FM instead, but as I said earlier, I forgot to add the FM, so all I have is the Castrol fluid in there. Before my rear seat delete, the groaning noise would be present at low-speed turns. Now that I don't have rear seats, groan seems to be present at low speeds all the time.

https://www.ecstuning.com/BMW-E46-M3...Kit/ES2602524/

I took my car to a shop a while back (not BMW dealer) to try to get motor and transmission mounts replaced through third party warranty, and the manager told me that the gears inside my transmission and differential were coming apart. I told him to **** himself.
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Old 03-09-2016, 12:57 PM   #7
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This is the email stating the trans and diff are dying from the inside. I'm really hoping this shop goes out of business.

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Old 03-09-2016, 12:59 PM   #8
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Old 03-10-2016, 02:04 AM   #9
bm_ch
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We are golden cows for some dealers...
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