[GeorgeSmooth]

After fitting the M3 diff to my car with a 3.85 ratio I can conclude that there is a significant performance drop. Everyone on the board did not recommend it but I tried anyway. There is a strange relation between applied torque on the road which should theoretically increase with a shorter ratio but it did not seem this was the case. It is strange that this occurs succesfully on NA cars.
I have now managed to source a DCT diff which has a 3.15 ratio, this is slightly higher than the 335 manual diff ratio.
Do you guys think I am taking a step backward or should I rather stick to the stock ratio? I would appreciate it if the guys that have fitted the manual ratio in there auto chime in with there experiences.

[shifterboy45]

Originally Posted by GeorgeSmooth

After fitting the M3 diff to my car with a 3.85 ratio I can conclude that there is a significant performance drop. Everyone on the board did not recommend it but I tried anyway. There is a strange relation between applied torque on the road which should theoretically increase with a shorter ratio but it did not seem this was the case. It is strange that this occurs succesfully on NA cars.
I have now managed to source a DCT diff which has a 3.15 ratio, this is slightly higher than the 335 manual diff ratio.
Do you guys think I am taking a step backward or should I rather stick to the stock ratio? I would appreciate it if the guys that have fitted the manual ratio in there auto chime in with there experiences.

experimenting with final drive ratios are fun and challenging -- when looking at making a change remember the there are a lot of factors to consider. some of them are:

engine effective torque band --
transmission drive ratio -- individual gearing 1/2/3/4/5/6
final drive ratio...

if you are looking to decrease your 1/4 mi time and keep some type of drivability, there will be a substantial sacrifice in overall performance, which does not translate to the street-- for those few seconds you need different setup to produce good results.. but dont think for a minute its going to be "drivable"..

plus, with the final gearing for a car the operates on average 3-4k RPMS higher, you are closing the window on useable torque at lower speeds .. very rarely are you pushing 5500-6000 rpm on your engine unless your are just short of WOT, while the M3 just gets smoothed out around that area. finding the right combo will take some experimenting ... the more people do it, the more information on what works and what doesnt will surface.. sorry for the non-answer, the available data is not conclusive to say the least.

[Mr. 5]

I've always said that cars with higher torque will benefit from a lower ratio rear end.
If there was any way that I could go lower than 3.08 then I would.

You're correct though George. If you are looking at a higher hp high redline low torque car, then the shorter gears are better.
I loved my 4.10s in my e46 M3.

[hotrod182]

I was Vbox testing the other week. 12.1 ET at 118.7mph. 3.7 sec 0-60, (on tune/dci/fuel on drag radials.) I tried launches in 1st gear and 2nd gear. Even though my 60' time was up to .10 second faster launching in 1st gear, my overall ET was the same. What I lost in the initial launch in 2nd gear, was made up by not having to waste time with a 1-2 shift. At higher traction levels, then 1st gear would decidedly have an advantage. But at my levels of performance, it didn't make any difference, and the 2nd gear launch was easier to replicate consistent results. Just goes to show the engine has quite a bit of torque, and doesn't mind taller gearing.

[chromisdesigns]

I think the difference between your N54 and what a normally aspirated engine would do is that the N54 produces max torque very quickly as the rpm increases, then holds it for a long time. So the higher gearing isn't pushing the engine into the torquey part of the rpm curve, which it would generally do in a normally aspirated car. You are already there, so there isn't that much gain.

[AndreM818]

Originally Posted by GeorgeSmooth

After fitting the M3 diff to my car with a 3.85 ratio I can conclude that there is a significant performance drop. Everyone on the board did not recommend it but I tried anyway. There is a strange relation between applied torque on the road which should theoretically increase with a shorter ratio but it did not seem this was the case. It is strange that this occurs succesfully on NA cars.
I have now managed to source a DCT diff which has a 3.15 ratio, this is slightly higher than the 335 manual diff ratio.
Do you guys think I am taking a step backward or should I rather stick to the stock ratio? I would appreciate it if the guys that have fitted the manual ratio in there auto chime in with there experiences.

E92 M3 diff.?

Originally Posted by Mr. 5

I've always said that cars with higher torque will benefit from a lower ratio rear end.
If there was any way that I could go lower than 3.08 then I would.

You're correct though George. If you are looking at a higher hp high redline low torque car, then the shorter gears are better.
I loved my 4.10s in my e46 M3.

Can you fit a differential with 3.08 on an e92 335i auto? Or is that only for sedans. By going with a 3.15, what will i benefit from stock. (sorry if its a dumb question)

[GeorgeSmooth]

Originally Posted by AndreM818

E92 M3 diff.?



Can you fit a differential with 3.08 on an e92 335i auto? Or is that only for sedans. By going with a 3.15, what will i benefit from stock. (sorry if its a dumb question)

@Andre The diff is indeed from a E92 M3. When I swop diffs again I will take a lot of pictures in regard to the mods that are needed and update my install thread. Then everyone can see what it entails.

The 3.08 ratio is the one found on the manual 335 vs 3.46 on the auto.

[M&M]

Georgie, I ran a simulation to work out the ultimate final drive ratio for a modded 335 at altitude & the simulator reckon 2.9 is the best ratio.

[GeorgeSmooth]

Originally Posted by M&M

Georgie, I ran a simulation to work out the ultimate final drive ratio for a modded 335 at altitude & the simulator reckon 2.9 is the best ratio.

Oh that simulation software. What wkw did you do it at? I should be around 380whp on 98.

[GeorgeSmooth]

Originally Posted by Mr. 5

I've always said that cars with higher torque will benefit from a lower ratio rear end.
If there was any way that I could go lower than 3.08 then I would.

You're correct though George. If you are looking at a higher hp high redline low torque car, then the shorter gears are better.
I loved my 4.10s in my e46 M3.

I managed to fit the 3.15. Thanks to M&M for the swop. I am really loving it, the car feels like its loading the turbos more and the power is great. Not sure what the times are going to look like and the average VBox G's but I should get to testing a bit soon.

Originally Posted by hotrod182

I was Vbox testing the other week. 12.1 ET at 118.7mph. 3.7 sec 0-60, (on tune/dci/fuel on drag radials.) I tried launches in 1st gear and 2nd gear. Even though my 60' time was up to .10 second faster launching in 1st gear, my overall ET was the same. What I lost in the initial launch in 2nd gear, was made up by not having to waste time with a 1-2 shift. At higher traction levels, then 1st gear would decidedly have an advantage. But at my levels of performance, it didn't make any difference, and the 2nd gear launch was easier to replicate consistent results. Just goes to show the engine has quite a bit of torque, and doesn't mind taller gearing.

Hotrod would you be able to send me a Vbox file of one of your low 12 second runs. If possible one using first and second and one using second. We battle to get traction here in SA and currently the best quarter mile is 12.5. It would be nice to see what kind of G's your car pulls on the first two gears when traction is available. I normally get a glimpse of .75g in first but then traction lets go and the gear averages very low - thats on a 12.7 run with a 2.00 60ft. If you keen pm me your email address so I can send you mine. Thanks.

[tryffis]

So reviving old thread; since im in middle of similar issue with diffs.

I managed to blow my oem stock diff and possibly half shaft along, so i've been thinking to fit whole m3 rear subframe with everything, atleast no more shaft issues hopefully.

My car is auto, and since i got 2 options, 3.15 and 3.85 to choose from so just wondering if anyone else has experiences with the 3.85 on auto?

Just wondering since nowdays you can modify shift points, skip 1st gear etc with xhp easily, would the short ratio be so bad idea anymore?

[type-dRew]

Originally Posted by tryffis

So reviving old thread; since im in middle of similar issue with diffs.

I managed to blow my oem stock diff and possibly half shaft along, so i've been thinking to fit whole m3 rear subframe with everything, atleast no more shaft issues hopefully.

My car is auto, and since i got 2 options, 3.15 and 3.85 to choose from so just wondering if anyone else has experiences with the 3.85 on auto?

Just wondering since nowdays you can modify shift points, skip 1st gear etc with xhp easily, would the short ratio be so bad idea anymore?

unless you have afteramarket turbos i wouldnt

wide open, every shift is going to drop you too high in the power band to keep the car quick with stock turbos

[feuer]

Originally Posted by tryffis

So reviving old thread; since im in middle of similar issue with diffs.

I managed to blow my oem stock diff and possibly half shaft along, so i've been thinking to fit whole m3 rear subframe with everything, atleast no more shaft issues hopefully.

My car is auto, and since i got 2 options, 3.15 and 3.85 to choose from so just wondering if anyone else has experiences with the 3.85 on auto?

Just wondering since nowdays you can modify shift points, skip 1st gear etc with xhp easily, would the short ratio be so bad idea anymore?

E60 m5 3.64 would be ok with 335i at.

[streetpro]

M diffs have different axle carriers, you would have to swap the whole rear... leaving behind the fact that to buy and install "a used M diff, possibly working" is not exactly a win-win in a longer run, they either have/develop a play and start to loose the lock ability (inside is a silicon sheer pump type unit that is sealed with tiny large o-rings that start to leak).

[feuer]

Originally Posted by streetpro

M diffs have different axle carriers, you would have to swap the whole rear... leaving behind the fact that to buy and install "a used M diff, possibly working" is not exactly a win-win in a longer run, they either have/develop a play and start to loose the lock ability (inside is a silicon sheer pump type unit that is sealed with tiny large o-rings that start to leak).

The half axles from M3 fit, the drive shaft would nee to be custom made, and yes, M LSD aren't known to last very long, however, allows for a lot of aftermarket replacement. Won't be cheap....

[tryffis]

Originally Posted by feuer

The half axles from M3 fit, the drive shaft would nee to be custom made, and yes, M LSD aren't known to last very long, however, allows for a lot of aftermarket replacement. Won't be cheap....

So basically i managed to find whole subframe( all the arms, hubs, brakes, shafts, diff etc) + prop with everything still connected for really good price, and been driven less than 30k km, and by the looks of it, its most likely truthful. I asked local propshaft specialist, and he called 250€ for the welding and balancing.
For the suspension i've been thinking going bilstein b8 and eibach prokit set so basically "b12". They sell front and rear pairs seperately. Getting the rear ones first, leaving myself option to go maybe m3 front aswell later on.

Possibly my current diff is damaged at pinion and ring also. So basically going torsen way, it would require whole pumpkin with lsd (2000-2500€) + rear bushings 250€, remanufactured axle shafts 400€, and new wheel bearings just because already getting everything apart. And since that m3 unit is complete, there is alot less costs on installing everything.

Still would'nt have all other upgrades coming along, suspension, brakes etc.

Now i'm wondering about other possible issue with this setup,
I looked some specs from https://www.ultimatespecs.com/, and found out that according to this there is 32mm difference on the rear track width between 335 and m3 idk how to confirm that data or how is it measured, but if that is correct that is going to cause some serious fitting issues since im already really tight with little rolling, 10,5" et 22 rear

Oh and a picture from the current state https://ibb.co/Tbdd2Tf

[dr.rabia.e92]

do you thing that MT m3 diff 3.85 fit on dct 335 ?
what are the pros and cons ?