Differential Time, 3.91 vs 4.10 on 6 speed ZCP

[Silbergrau metallic]

I know this has been discussed, probably at nauseum, but It's time for me to have my Diff rebuilt on my 2005 M3 ZCP with a 6 Speed and I'm considering Diffsonline with the Wavetrac LSD. Just curious of what Gear ratio people on here prefer and why. I was thinking of going 4.10 and some people seem to love that ratio, but there have also been some that considered it a not so good Ratio for whatever reason that is. I heard that for 6 speed cars, the 4.10 is the one to go with and 3.91 for SMG cars, but I was wondering if 3.91 would be the sweet spot, since my car's tune has removed the Speed limiter, so my Top speed will not be affected so much, but some gains in acceleration. So! before I spend $5000 plus on this thing, I want to know the Pro's and Con's of each ratio. My worry is that with the 4.10, my 1st gear would be useless. My Mods currently are full Supersprint exhaust, Eventuri Intake, DUDMD tune, HR Sway Bars and Wheel spacers and DMG front and rear strut. Any suggestions from the experts will be so much appreciated.

[oceansize]

https://nam3forum.com/forums/forum/m...3-62-3-91-4-10

I went 3.91 and like it. Street driven SMG and supercharged so I violated every key tenet of na e46dom. Don't listen to me.

[Tbonem3]

Stock. Unless your track is hilly and/or tight or you auto-x, then gear lower.

[heinzboehmer]

6MT and SMG have the same gear ratios in the transmission (it's actually the same transmission), so that shouldn't affect anything. I like stock too

[Obioban]

I swapped out my LSD for a wavetrac, but kept final drive ratio stock. BMW just perfectly nailed it with the stock gearing, IMO.

[sapote]

It's time for me to have my Diff rebuilt on my 2005 M3 ZCP with a 6 Speed and I'm considering Diffsonline with the Wavetrac LSD..

So you are going to swap out the stock carrier (probably version 2 which requires special tool to open) with a Wavetrac? Is this include the 4 spiders and the two side-gears? I want the old carrier, for experiment, if you're going to trash it.

[Silbergrau metallic]

So you are going to swap out the stock carrier (probably version 2 which requires special tool to open) with a Wavetrac? Is this include the 4 spiders and the two side-gears? I want the old carrier, for experiment, if you're going to trash it.

I'm not sure, are you saying that there is a special Wavetrack carrier that needs to be used when going to a Wavetrac LSD and if that's the case, do you know what it looks like. I decided that I was going to go with the Wavetrac, because most enthusiasts seem to like them, but I'm unaware of any other special parts that are needed to do the install. Sorry, I'm a bit of a Newb here.

[Obioban]

So you are going to swap out the stock carrier (probably version 2 which requires special tool to open) with a Wavetrac? Is this include the 4 spiders and the two side-gears? I want the old carrier, for experiment, if you're going to trash it.

If he’s using diffsonline, they’ll use a carrier they have on hand and use his original as a core.

[sapote]

I'm not sure, are you saying that there is a special Wavetrack carrier that needs to be used when going to a Wavetrac LSD and if that's the case, do you know what it looks like. I decided that I was going to go with the Wavetrac, because most enthusiasts seem to like them, but I'm unaware of any other special parts that are needed to do the install. Sorry, I'm a bit of a Newb here.

My understanding is that Wavetrac provides the carriers for our cars and other makes too. The shop or Diiffonline in this case will buy and install Wavetrac carrier into the original M3 diff housing and probably toss out the original stock M3 carrier. I thought you are going to buy the Wavetrac carrier and swap out yourself.

Wavetrac carrier (not necessary the right carrier for E46 M3):

http://www.wavetrac.net/images/02M_blk_325.jpg

[maupineda]

4.1, 3.91 is only 8% shorter, if you want to feel an actual difference go to 4.1.

and no, BMW did not nail it, the ratios are too long for an 8k redline engine. Top speed should be achieved in top gear, and with the OE final drive it would do 200mph, so is too long for the capability of the engine and chassis. 4.1 would put you 174mph top speed, more inline with what the car can handle and you will enjoy the added torque to the wheels.

also, you will still have a true 6 spd car, that thing that 1st is useless is not accurate.

I have 4.1

another alternative is, go with 3.91 and put 19 with stock tire size, this gives a 4% higher final drive (almost same as a 4.1 diff), if you don't like you can go back to stock 18 sizes for the 8% shorter drive experience. This would be the only benefit I would see in going for 3.91, gives you som flexibility.

[Obioban]

4.1, 3.91 is only 8% shorter, if you want to feel an actual difference go to 4.1.

and no, BMW did not nail it, the ratios are too long for an 8k redline engine. Top speed should be achieved in top gear, and with the OE final drive it would do 200mph, so is too long for the capability of the engine and chassis. 4.1 would put you 174mph top speed, more inline with what the car can handle and you will enjoy the added torque to the wheels.

I already long for a 7th gear on the highway, with stock gearing. Stilling at 3500rpm at 80 in 5th (top gear) was my single most hated aspect of my e36 M3. Zero desire to recreate that in my e46.

If I want more torque to the wheels, I’ll downshift 😜

[old///MFanatic]

It really depends on your car’s use and then your preference.

Also it’s really silly when you hear people without a 4.10 say stuff about 1st gear. First gear is fine unless you drive only in first and need to go over 30mph.

For the record I have the 4.10 from BMW Motorsport and love it.

[Obioban]

It really depends on your car’s use and then your preference.

Also it’s really silly when you hear people without a 4.10 say stuff about 1st gear. First gear is fine unless you drive only in first and need to go over 30mph.

For the record I have the 4.10 from BMW Motorsport and love it.

… and your cars weight and power. I can only floor it in first in ideal conditions without lighting them up, with stock gearing, with 350rwhp and <3100 lbs.

[Altaran]

And depends where you drive it. Personally I will switch to a 3.91 with a Drexler 8 plate slip unit soon, as it works better on the ring.
Other tracks may favor a 4.1 with the power/weight the car has.
That's why BMW Motorsport has both options available, race teams switch setup depending on track.
There is no single best solution.

Edit: if I were to drive only on the street I would stick with the stock gearing.

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[Syfon]

Stock gearing is too tall imho. I'll build a diff soon enough with 4.10 gears and euro e36 m3 evo centre.