Need Differential Rebuild Recommendations

[ThatDudeZac]

Hello, my first post here and this forum seems to have a much more active member group than Facebook groups or other m3 forums. So I am hopping to finally find some solutions or advice on the route to go to get my worn e46 m3s differential rebuilt for the track, including driving to the track.

There doesnt seem to be alot of newer info out there on this topic but from what I could dig up, it seems the tried and true standard in Europe is the zf diff swap from e39 m5s or similar and changing ring and pinion to 4.10 or 3.91 gears. The prices I'm seeing vary from 2-4k euros fully built vs the other route is diffsonline but that's gonna cost me over $7500 with core charge, gearset and upgrade lsd selection. That seems a bit on the high end to me. I'd much rather source the parts my self and go to a local shop (DFW TX) to get this all done on a lower budget.

Now this is where the problem I'm running into is, finding a gearset (preferably 3.91) and the remaining lsd components. Ideally I'd love to go zf lsd and 3.91 but where is the best place to find these things and what all is needed? What's are yalls recommendations and or advice or even alternatives setups that yall had success with?

[ethan]

Couple other options include Wavetrac (search for Obioban's posts about his which he uses dual duty) and putting replacement clutches in your existing diff. There's an active thread about the latter. Question is how serious of a diff do you really need?

Consider which tracks you'll be driving before you change gearing. Stock is often a good choice and is excellent on the street, but 3.91 works well for me on the small club tracks I drive. 4.10 would likely make me slower.

[George Hill]

I'd much rather source the parts my self and go to a local shop (DFW TX) to get this all done on a lower budget.

Find the shop willing to take on this project first and then do what they say.

[elrichmeister]

Following this thread. Im also researching this same topic.
The most recommendations, even from my local shop was to get one from Diffs Online.

I'm leaning towards Diffs online with 3.91 M-Variable Mainly for convivence and piece of mind that the diff was rebuilt well.
Another alternative is to source ring an pinion to desired ratio, and get a rebuild kit from racing diffs (not sure on quality of these) that has clutches, seals and bearings, and finding a shop to do the rebuild, or like mentioned above have them source stuff for you.
you can find the ring and pinion from Peaky Parts, they have some on ebay.

[jayjaya29]

Following this thread. Im also researching this same topic.
The most recommendations, even from my local shop was to get one from Diffs Online.

I'm leaning towards Diffs online with 3.91 M-Variable Mainly for convivence and piece of mind that the diff was rebuilt well.
Another alternative is to source ring an pinion to desired ratio, and get a rebuild kit from racing diffs (not sure on quality of these) that has clutches, seals and bearings, and finding a shop to do the rebuild, or like mentioned above have them source stuff for you.
you can find the ring and pinion from Peaky Parts, they have some on ebay.

Racing diff's parts are known to be junk. Hence their attractive price.

[ThatDudeZac]

Following this thread. Im also researching this same topic.
The most recommendations, even from my local shop was to get one from Diffs Online.

I'm leaning towards Diffs online with 3.91 M-Variable Mainly for convivence and piece of mind that the diff was rebuilt well.
Another alternative is to source ring an pinion to desired ratio, and get a rebuild kit from racing diffs (not sure on quality of these) that has clutches, seals and bearings, and finding a shop to do the rebuild, or like mentioned above have them source stuff for you.
you can find the ring and pinion from Peaky Parts, they have some on ebay.

I actually messaged them on Instagram a little earlier today, I saw they had zf diffs and 3.91 ring and pinion hopefully they can help sort me out!

[ThatDudeZac]

Couple other options include Wavetrac (search for Obioban's posts about his which he uses dual duty) and putting replacement clutches in your existing diff. There's an active thread about the latter. Question is how serious of a diff do you really need?

Consider which tracks you'll be driving before you change gearing. Stock is often a good choice and is excellent on the street, but 3.91 works well for me on the small club tracks I drive. 4.10 would likely make me slower.

Yea that's why I'm going for 3.91 the tracks around me, Eagles canyon and Cresson both would work for 4.10 or 3.91 but I don't wanna deal with 5k rpm in 6th trying to drive to the tracks lol

I was told via e46 m3 track group on fb to not go with a wavetrac or helical types, even though they are supposedly maintainance free the locking/slip aspect is worse than the m-variable 🤷♂️

[0-60motorsports]

F it im getting a wavetrack and then also putting back the 3.62 gears (if i can find a mint set)....and if i cant i'll just stick to my 3.91 gearset thats already in there.

[maupineda]

F it im getting a wavetrack and then also putting back the 3.62 gears (if i can find a mint set)....and if i cant i'll just stick to my 3.91 gearset thats already in there.

Want the 3.62 I took off for my 4.1 rebuild?

[0-60motorsports]

Want the 3.62 I took off for my 4.1 rebuild?

I'll message you.

[bigjae46]

You can source Timken bearings from Amazon - it was about $150 the last time I checked. Probably a little more now. Then you need the seals, o-rings, crush sleeve, and ring gear bolts - $250, 3.91 gear set - about $1100 from the dealer, ZF LSD - $1000 to $1500 used on eBay. Equal length axle shafts - $400/pr new from dealer

So $3.5k total.

Racing Diffs has a 4 clutch conversion for the ZF, works fine. They also have pressure plates with variable ramps machined in...not sure about that. I may give it a try at some point.

I'm in Houston, I have a guy that can build the diff if you supply the core and parts. $400-$500.

[ChapterM3]

Following for future reference! Good thread for 2025

[EthanolTurbo]

Following this thread. Im also researching this same topic.
The most recommendations, even from my local shop was to get one from Diffs Online.

I'm leaning towards Diffs online with 3.91 M-Variable Mainly for convivence and piece of mind that the diff was rebuilt well.
Another alternative is to source ring an pinion to desired ratio, and get a rebuild kit from racing diffs (not sure on quality of these) that has clutches, seals and bearings, and finding a shop to do the rebuild, or like mentioned above have them source stuff for you.
you can find the ring and pinion from Peaky Parts, they have some on ebay.

Waste of time. Take it to Pro Gear in San Diego, they do a full rebuild including all parts for under $900.

[EthanolTurbo]

F it im getting a wavetrack and then also putting back the 3.62 gears (if i can find a mint set)....and if i cant i'll just stick to my 3.91 gearset thats already in there.

Wavetrac is junk, Drexler is by far the best option for these cars.

[0-60motorsports]

Wavetrac is junk, Drexler is by far the best option for these cars.

Are you talking about for turbo cars or NA cars? What's the price difference?