[Heitzer]

I am used to changing drive ratios on my motorcycles (very easy with sprockets). It's more fun to rev through the rpm range and you have more thrust. How could I do that on my 235i? Change differential or get an LSD modified?

This has been done in the 3 and 1 series with success apparently. Some really liked going from 3.08 to 3.46 (same as automatic actually) by modifying ratios in the LSD .
http://www.vacmotorsports.com/blog/3...no-lsd-really/

Others used the differential (non-LSD) from another model type -- older 3 series cars for example. Looking at all 2 series model types for final drive ratios the diesel 220d for example has a 3.231 drive ratio (comparison table for manual cars are below -the automatic 2 series are all 3.077 I believe). Close but may be not perfect. Or one from a 228i at 3.99 (seems very high). Or would automatic differentials fit from 1 series or 3 series to get a 3.46 ratio?

So many unanswered questions. Most important - would I actually like it with an aggressive ratio of 3.46 or more? Hope someone has tried this already or has ideas.

[Liquidpaper]

Originally Posted by Heitzer

I am used to changing drive ratios on my motorcycles (very easy with sprockets). It's more fun to rev through the rpm range and you have more thrust. How could I do that on my 235i? Change differential or get an LSD modified?

This has been done in the 3 and 1 series with success apparently. Some really liked going from 3.08 to 3.46 (same as automatic actually) by modifying ratios in the LSD .
http://www.vacmotorsports.com/blog/3...no-lsd-really/

Others used the differential (non-LSD) from another model type -- older 3 series cars for example. Looking at all 2 series model types for final drive ratios the diesel 220d for example has a 3.231 drive ratio (comparison table for manual cars are below -the automatic 2 series are all 3.077 I believe). Close but may be not perfect. Or one from a 228i at 3.99 (seems very high). Or would automatic differentials fit from 1 series or 3 series to get a 3.46 ratio?

So many unanswered questions. Most important - would I actually like it with an aggressive ratio of 3.46 or more? Hope someone has tried this already or has ideas.

I'm about to do this in two weeks (brand new diff from Diffsonline). I'll post a review.

[Heitzer]

Terrific. What ratio are you going with?

[3.0L]

This is a way back experience. I recall people running 4.11 rear-end gears back in the '60's, and those muscle cars were really quick. Problem was, with only 4-speed manuals, the engine was pretty wound out on the freeway. Really impractical at the time.

[Liquidpaper]

Originally Posted by Heitzer

Terrific. What ratio are you going with?

3.46

[3.0L]

Originally Posted by Liquidpaper

3.46

Do you have an idea as to the performance increase in numbers? 0 to 60 times, etc.?

And what will your RPM be on the freeway in top gear at say, 70 MPH?

[Heitzer]

The ratio difference between 3.077 and 3.46 is 1.12. So you should have 12% more thrust throughout the rev range if my math is correct.

0-60 improvements should get close to the numbers the automatic pulls. Top speed in first and second gear is 35 and 53mph for the steptronic. The manual car has 41 and 72 stock which goes to 36.6 and 64.3mph with the 3.46 ratio. You have to do only 2 shifts manual but slightly lower gear ratios.

At 70mph the stock car runs 2473rpm in sixth gear. Should be 2781 after going 3.46. Not helping gas mileage for sure but not a giant difference either.

[Liquidpaper]

Originally Posted by 3.0L

Do you have an idea as to the performance increase in numbers? 0 to 60 times, etc.?

And what will your RPM be on the freeway in top gear at say, 70 MPH?

Its not too big a change -- just right if you ask me. See the attached sheet -- an M235i running 255/35/18 square (me) with a 3.46 rear end.

The drive ratio increase gives a 12% torque increase (3.46/3.08 = 1.12337) from mechanical advantage in every gear, so the acceleration increase should be significant. At 70 mph in 6th, you'll be at 2750 rpm.

[Boosted_six]

Interested to know what kind of money you are looking at for a 3.46 final with an LSD fitted?

Did you have to pay a core charge / core exchange?

[amw896]

don't mean to thread jack but have you looked at the m performance LSD? Would like to know why or why not? The previous owner of mine had this port installed and I think it's fantastic but I haven't ran a m235i without the LSD or a different brand.

[Heitzer]

Originally Posted by Boosted_six

Interested to know what kind of money you are looking at for a 3.46 final with an LSD fitted?

Did you have to pay a core charge / core exchange?

I finally did put in the wavetrac LSD with a 3.46 ratio last month. Had no time yet to write a report but the car is so much more fun now. Some of it is the LSD I think particular in the turns. The biggest change, adding the greatest smiles, is the extra thrust. It feels so much faster. More importantly, I can now rev the engine and have fun more consistently without going way overspeed.

Cost is $3000 before install (Diffsonline keeps the stock differential) . Turner Motorsport here in MA worked on the car and they did the lower control arms also which definitely increase fun during commuting and street driving. Very happy with advice and install from both.


This is the best mod for the car in my opinion. I followed LiquidPapers advice and am glad I did.

[Liquidpaper]

Originally Posted by Heitzer

I finally did put in the wavetrac LSD with a 3.46 ratio last month. Had no time yet to write a report but the car is so much more fun now. Some of it is the LSD I think particular in the turns. The biggest change, adding the greatest smiles, is the extra thrust. It feels so much faster. More importantly, I can now rev the engine and have fun more consistently without going way overspeed.

Cost is $3000 before install (Diffsonline keeps the stock differential) . Turner Motorsport here in MA worked on the car and they did the lower control arms also which definitely increase fun during commuting and street driving. Very happy with advice and install from both.


This is the best mod for the car in my opinion. I followed LiquidPapers advice and am glad I did.

It is without a doubt the best thing I have done to my car. Only regret is that I probably should have gone with a Wavetrac carrier (rather than the custom 3 clutch setup I ended up getting) due to cost (way cheaper). Glad you like yours. Dan does an excellent job.

[abirmaher]

Originally Posted by Heitzer

I finally did put in the wavetrac LSD with a 3.46 ratio last month. Had no time yet to write a report but the car is so much more fun now. Some of it is the LSD I think particular in the turns. The biggest change, adding the greatest smiles, is the extra thrust. It feels so much faster. More importantly, I can now rev the engine and have fun more consistently without going way overspeed.

Cost is $3000 before install (Diffsonline keeps the stock differential) . Turner Motorsport here in MA worked on the car and they did the lower control arms also which definitely increase fun during commuting and street driving. Very happy with advice and install from both.


This is the best mod for the car in my opinion. I followed LiquidPapers advice and am glad I did.

Is your car manual or auto? Sorry if I missed it in the thread.

[Heitzer]

It's manual. The auto with its eight speeds shifts much earlier and there is probably no use in changing final gear ratios. Or is there

[Redbeemer]

Originally Posted by Liquidpaper

Its not too big a change -- just right if you ask me. See the attached sheet -- an M235i running 255/35/18 square (me) with a 3.46 rear end.

The drive ratio increase gives a 12% torque increase (3.46/3.08 = 1.12337) from mechanical advantage in every gear, so the acceleration increase should be significant. At 70 mph in 6th, you'll be at 2750 rpm.

Sounds very interesting! I agree that a 3.46 ratio is probably a nice compromise for street use. One concern that I have that was not mentioned, however, is that changing the final drive ratio messes up the speedometer/odometer unless you install the corresponding gear drive for them (if they still use a gear since they are now electronic). Did you switch out the speedometer drive or are you just living with the fact that it is off a bit?

[Liquidpaper]

Originally Posted by Redbeemer

Sounds very interesting! I agree that a 3.46 ratio is probably a nice compromise for street use. One concern that I have that was not mentioned, however, is that changing the final drive ratio messes up the speedometer/odometer unless you install the corresponding gear drive for them (if they still use a gear since they are now electronic). Did you switch out the speedometer drive or are you just living with the fact that it is off a bit?

This car, like most modern cars, calculates speed based on wheel rotation. Therefore, switching out a final drive won't mess up your speedo -- the car will compensate because the wheels will be moving faster.

What does cause your car to have an inaccurate speed is wheel/tire size (rolling diameter). The car calculates speed based on wheel revolutions, so if your car has a larger rolling diameter, the wheels dont have to spin as fast to get to a certain speed, and the car will read "low" with respect to speedometer reading.

[Boosted_six]

Are the rear diffs and corisponding ratios the same between the M235i and M240i does any one know

[Heitzer]

M240i seems to have the same drive and final ratio as M235i. Source: Official german BMW press release.

[XutvJet]

I'd love to have the 3.46 rear gear as I feel the M235 gearing is just a tad too long. The M2 comes with a 3.46 gear. Interestingly, the R&T compare between the 228i, M235i, and M2 gives a gear by gear mph break down and I was surprised at the minimal difference in the max mph in gears 1, 2, and 3 between the M235 and M2 (they use the same 6MT and internal gearings). By the seat of the pants though, the 3.46 gear will feel a bit quicker. Will it translate to much improvement in the 1/4 mile? Doubtful. On a road course? Maybe, maybe not

http://www.roadandtrack.com/car-cult...mparison-test/

[Liquidpaper]

Originally Posted by XutvJet

I'd love to have the 3.46 rear gear as I feel the M235 gearing is just a tad too long. The M2 comes with a 3.46 gear. Interestingly, the R&T compare between the 228i, M235i, and M2 gives a gear by gear mph break down and I was surprised at the minimal difference in the max mph in gears 1, 2, and 3 between the M235 and M2 (they use the same 6MT and internal gearings). By the seat of the pants though, the 3.46 gear will feel a bit quicker. Will it translate to much improvement in the 1/4 mile? Doubtful. On a road course? Maybe, maybe not

http://www.roadandtrack.com/car-cult...mparison-test/

I think the M2 uses the 6 speed out of the M3/M4, which is not the same box as in the M235i, which might explain why the max-speeds come out the same even though the M2 has a shorter final drive.

When I had the 3.08 final drive, third gear red-lined at about 109 mph, which was a little too long for me. With the 3.46 final drive, third goes to about 95, which makes more sense.

With respect to it being "faster" it really depends. Your "in gear" acceleration will be faster because you have 12% more wheel-torque through mechanical advantage. Downside is that you have to shift "sooner". Some road courses I think the taller gears would be better (I've had to shift right before a breaking zone a few times or just bang into the rev limiter for a bit because of the shorter gearing), but others I think the shorter gears help (more technical courses where your top speed isn't quite as high).

Real race cars frequently change their final-drive and differential setup based on the course they are running, so you kind of have to just pick something and stay with it for a street car.

[XutvJet]

The 6MT box used is the M235 is the same dry sump ZF unit used in the 1M, M2, M3, and M4 according to GetBMWparts.com and various mags and BMW publicatuons. Internal gear ratios are all the same too among all cars. I wonder why you're only seeing 95mph in 3rd where as the M2 can see 103mph.

[Heitzer]

The difference is due to the larger diameter 19inch tires on the M2 I think. The Supersport tires run 790 revs per mile for the 265/35 ZR19 of the M2 compared to 840 revs on the M235i. That difference would lead to 36.7 mph in first gear instead of the 39 mph if you put the 18inch tires on the M2.

Clearly some of the performance advantage of the M2 is due to gearing. I am still in awe with the changes this made to my M235i. Highly recommend .