Do I need to change standard M3 rear diff if I'm planning to put 4.10 gears ? Rear end getting loose when I exiting corners because of excessive torque on read wheels with standard M3 LSD. It looks like there is not enough torque on inside wheels (wheels spinning when I put more gas making the car drifting) If I put 4.10 diff I'm afraid that problem might get even worse

Increasing the gear ratio will make it worse unless you learn how to modulate the power so you are not spinning your wheels.

Question is will LSD help ?

The car already comes with a LSD.

yes, but it does't seem to be effective on a track. It think it is way to soft

If you're drifting the rear end out, then you're already spinning both wheels and there's nothing wrong with the diff. If the diff were overly worn and acting more like an open diff, then giving it more gas coming out of the corner would simply spin the inside wheel and the rear end would be less likely to come around on you. Based on what you've described, there's nothing wrong with the diff you simply need to learn to modulate the throttle as Kevlar has suggested. A diff with more static lockup isn't going to help you, save your $$$.

yes, but it does't seem to be effective on a track. It think it is way to soft
It's been very effective for me when I was on the track... you can change it out for a unit with more lockup, but I think it will be a backwards move unless of course you are trying to do something "different" with the car that we are not understanding and in that case, it sounds like you are trying to use a hammer as a screwdriver.

Thanks, I think you are right

It's been very effective for me when I was on the track... you can change it out for a unit with more lockup, but I think it will be a backwards move unless of course you are trying to do something "different" with the car that we are not understanding and in that case, it sounds like you are trying to use a hammer as a screwdriver.

Oh yeah, breakin the back end loose is just part of owning an M3... Its not the worst about that but she'll go sideways if you're not careful. The more lockup you get, the greater your chances of sliding... the less lockup you get the less your chances of sliding. I.E. - locked rear end vs. open...

On a scale from most lock up and most sliding to least...

Locked Diff --> Limited Slip Diff --> Open Diff
Sliding Alot --> Limited Sliding --> No Sliding

If you really wanted to stop sliding everywhere, turn DOWN the lock up so that the wheel with least resistance gets more power and the wheel with traction gets less. That way the wheel with traction doesnt get enough power to lose traction.

The M-Variable Diff in our cars is one of the most advanced LSD's in a production sports car today. It has been a characteristic of all M's since their inception and will run wonderfully on a track.

Kevlar is right, focus on throttle control and pedal modulation. You want to have already downshifted into your gear while braking before entering the turn. Once you have come into the turn use the throttle to carry you through the apex and through your exit.

You have to remember. You only have so much traction to work with. Any traction you are using for braking, you can not use to turn; and vice versa. Any traction you use for turning, you can not use for acceleration; and vice versa. So as you enter the turn, you want to complete the majority of your braking before you start turning. Through the apex you want to complete the majority of your turning before you start accelerating hard. And then as you exit, get back on the throttle and watch your pedal modulation as you put it back into full force so that you dont kick it sideways coming out of the turn.

You dont want to brake super late and cut into the turn and then get back on the throttle. You will be spreading what little traction you have too thin too quickly and you will be throwing the weight of the vehicle around and screwing with your balance. Sure you may enter the turn much faster, but then you are braking while turning and when you should be getting back on the throttle you are fighting to hold your line while on the brake, and then you wont be able to get back on the throttle until after the apex where you will go full throttle to make up for the slow turn and kick it sideways.

I had a problem with this where i felt it was necessary to enter the turn as quickly as possible, brake as late as possible, and just heel-toe shift while entering the turn to save time and then get back on the gas on the way out. I ended up entering too quickly fighting to stay in my line, slowing down way too much and then going full throttle to get back my time and slipping on the way out. A buddy of mine that actually races taught me to get into gear before the turn, trail-brake into the turn and then use the throttle to carry me smoothly into and out of the turn.

Just curious, will the 4.10 gears give you a higher top speed? Also, how do you plan to do this, just change the last gear? I know very little about gearnig.

Just curious, will the 4.10 gears give you a higher top speed? Also, how do you plan to do this, just change the last gear? I know very little about gearnig.
The higher the number ... the lower your theoretical top speed. With a 3.64 gearing (stock), the cars theoretical top speed is 203mph. Now, we all know it will never reach that theoretical speed due to wind resistance versus horsepower. If you raise the gearing to a 3.91 or a 4.10, your theoretical top speed drops from 203 to 190ish and low 180s accordingly. However, because you are turning more RPM at any given point in time and making more power for any given speed, you may see increased acceleration up until your actual top speed.

By actual top speed, I mean where the amount of horsepower that you are making versus the amount of wind resistance you are fighting off. Everytime you double your rate of speed, the horsepower needed to overcome wind resistance quadruples.

awesome thread guys...thanks for the knowledge...I just bought an 01 M3, unfortunately I had to buy a convertible, because it was a great deal.... I want to really turn up the power on it, you guys seem quite knowledgeable in this field...I am brand new to threads/forums and don't, know much about them, I do know alot a fair amount about cars, but I grew up rebuilding 67 chevelles and 69 vettes, so electronics boggle me..lol. I am looking to stay sleeper and just add power, any and all help would be greatly appreciated, I also wanted to add a gauge pod under the radio and climate control in the cubby bin, any suggestions on that would be awesome too..thanks again...look forward to reading more.

Everytime you double your rate of speed, the horsepower needed to overcome wind resistance quadruples.

true, but the reason would be: aerodynamic drag quadruples with the doubling of speed. so to go twice as fast, means 4 times as much aero drag, which basically equates to needing 4 times as much horsepower. were saying the same thing, its just that when you approach it from a problem solving standpoint, you are trying to solve: power required for aerodrag(x)@speed(y) when x=frontal area times drag coeffiecent.

aww, my first post and i didnt even contribute to the original point of the thread :(

soo, does anyone know if the electro-hydraulic diff is controlled be the dme, or uses its own computer module? (i would think the later) and, im assuming its pulls data from the other systems (traction control, stability control, dme) for data? (steering angle, speed, yaw rate, throttle angle, ect)

The differential has no computer/electronic control module. It works of a set of hydraulic pumps in the unit itself. The DME can only interfere with it through use of the ABS system to use the brakes to slow a spinning tire or through reducing power to lessen power being fed to the differential.

PS... thanks for clarifying.

ahh, thanks, so its not active. no problem, i hope it didnt come across as rude. hi btw :)

Now... the new differentials in the X6 use an active electronic differential to help steer the car during adverse conditions. It is called "Torque Vectoring"

I just put a 4.10 with a quaife differential. It's night and day. Unreal. that's all I have to say. spend the extra bucks, wait if you have to cause it will be worth it. I promise.

Dang, HiRide makes me want to go to the track!!

TommyGM3, never be sad cause you "had" to buy a convertible. Unless you bought it as a track car, the drop top is far more functional every day that the slightly faster more rigid coupe. At least that is my opinion.

You bought a covertible, now just put a Horsepowerfreaks turbo kit in it and you will far exceed all your expectations for performance.

I just put a 4.10 with a quaife differential. It's night and day. Unreal. that's all I have to say. spend the extra bucks, wait if you have to cause it will be worth it. I promise.

Please explain, expand, what its doing for you. Is it the straight line acceleration or around the track. I've been considering this thinking it will leave me at higher RPM's while exiting turns thus more power when I want FOT. On the other hand I think that if I was more technically sound in taking the turns I'd be exiting faster anyway.

Summary of Kevlar and HiRide's posts:

...On the other hand I think that if I was more technically sound in taking the turns I'd be exiting faster anyway.

:devillook

but yeah, now that you installed the quaife -- what's the driving difference between the two?

Great topic. I was considering doing this to my e36 M3 when I had it but I think I def want to do this when I eventually get my e46 M3. 4.10 gears all the way and keep it NA horsepower.

PS: this is prob a stretch but does anybody have or have seen video of the speedo of an M3 with 4.10 gears? I would love to see this.

Please explain, expand, what its doing for you. Is it the straight line acceleration or around the track. I've been considering this thinking it will leave me at higher RPM's while exiting turns thus more power when I want FOT. On the other hand I think that if I was more technically sound in taking the turns I'd be exiting faster anyway.

Well the 4.10 will actually apply 10+% more torque to the wheels....thus creating a situation more likely to lose traction. The quaife is a gear driven Diff., as opposed to the other diffs that use like pads or clutch type plate to lock up the right and left side. The Quaife will actually creat a 50-50 split from the go but in turns it will be less likely to try to lock under tire slippage. Therefore allowing to the outside tire to rotate quicker than the inside and create a much better tracking around the turn under heavy acceleration. I am no mechanic and if anyone knows more than me feel free to chime in.. I'm trying to explain it to the best I understand it and how it was explained to me. I have no track time with the setup but road driving it makes a very very noticeable difference in control and feel. The car tracks in turns on rails. I have UnderDrive pulleys.......and then intake, maf, exhaust and stage 3 s/w all Dinan. Just Dinan struts for my suspension. and this cars STICKS... The power to the road is much more readily available at lower speeds and it RIPS... Man best upgrade I've ever seen. Wouldn't do the 4.10 w/o the Quaife for just the mere reason that the torque delivery is so much stronger. I hope this helped a bit.

Great topic. I was considering doing this to my e36 M3 when I had it but I think I def want to do this when I eventually get my e46 M3. 4.10 gears all the way and keep it NA horsepower.

PS: this is prob a stretch but does anybody have or have seen video of the speedo of an M3 with 4.10 gears? I would love to see this.

I'll post a video as soon as I can.

search for b0ki he has 4.10 as well as intake/headers/exhaust/pulleys/software + nitrous.

so he is making 310RWHP with 4.10 + 100shot of nitrous. He is ridiculously fast and outruns every SC E46 M3 around here. although I think he is running a 150 or 200 shot now. At one point he ran C16 fuel and leaned out the nitrous even farther with the higher octane fuel. He apparently made 524 RWHP on the dyno NA with that setup but never ran it on the street. I dont blame him, thats for the dyno only....

http://www.youtube.com/watch?v=REhyIQy1qYs&feature=related

look for assosiated vids... this one is really really old. his rims are still silver in this.