Bernanke

hey guys, Im planning on doing differential, I can get differential and LSD taken care of myself but i still cannot find anyone who can reprogram the tranny computer to accept the new gearing so the car does not essentially go into limp mode. Does anyone know any companies that can do it locally in AZ or TX, if not then who can do it across the country?

stevebez

MKB are only guys I know of as they remap their trannies for their shorter diff ratios.

Rgds Steve.

Jakpro1

Casper356 said Renntech does it.
That was for SL/S65 tranny of course.....gotta be doable on the E.

DJE55

This has to do with building up the internals of the tranny to handle more power. He's changing the gear ratio in the rear and needs the computer to be remapped to accept the new ratio. I don't think this has anything to do with what he's looking for? I could be wrong though, and it wouldn't be the first time.

ClayJ

MKB for sure, and maybe Renntech.

I don't believe that either Kleeman or Brabus do this.....

mclarenm8d

Guys, help me out here ...

Has anyone actually tried to change the rear diff ratios to confirm that the Tranny ECU will panic, or is this just a rumor spread by tuners to get us to pay for something we don't need?

Normally, tranny ECU's (TCU) keep track of input shaft speed, output shaft speed, and the gear they are in. If there is a mismatch, it will cause a limp home mode because it is interpreted as massive slippage/lock-up. This is why we can't change the internal ratios of the tranny or use a different MB five speed tranny with different internal ratios. The stock TCU will freak.

But the rear diff ratio is separate, and really the tranny ECU doesn't need to care. I can see the CAN-BUS info between the ECU and TCU enabling the recognition of mismatch in vehicle speeds, but that normally doesn't matter.

Is the MPH being determined from driveshaft speed/output shaft speed of the tranny, or from the axle speed?

BMW guys with the same basic Bosch architecture do this type of swap all the time without any need for ECU/TCU work. Heck, they don't even have to worry about speedo calibration because the speedo signal comes off the axle.

dasrok8

Are you sure the Bimmers aren't 6 speeds? As in no trans ECU needed.
Vettes Vipers, Cobras etc., all sticks need no programming.
Auto trans vettes need to be reprogrammed. The tranny ECU reads pulses per degree of rotation from input given by wheel speed sensors. It's just a calibration factor, like changing tire diameters. A hypertech (or comparable)type of product should be able to adjust the tranny ECU.
Good luck
George

mclarenm8d

It's almost a "standard" thing for guys with automatic BMW 840/850's to do. Now, I am feeling lazy so I didn't check my wiring diagrams for 840/850's, but I did check for Audis (Bosch ECU and TCU controllers), and the vehicle speed sensor is not a direct input into the TCU. But at least it is off of the axle as I had expected, so if one wanted to go through the hassle of an AWD final drive ratio conversion at least the speedo would be accurate.

My 840/850 diagrams are on paper ... Audi stuff is on my CD's, much easier searching :-).

Now, if I could only get my hands on the wiring diagram for our cars !! I agree with where I think you are going with the hypertech reference, either way this should be something that is simple for a rear-wheel drive car.

OmeyHomey, getting back to your original post, I should mention that I am interested in what you discover on this as I see this as a big bang for the buck. Taking our 2.65:1 and going to ~3.10:1 and raising the rev limiter to 6900 RPM would take away some of the torque advantage the turbo V12's have.

More importantly for my tastes, it would make the car funner to drive. I've gotten myself in trouble with local law enforcement twice trying to run my CL55 through the gears at only half throttle ... with the 2.65's, one can only do the 1-2 shift before bustin' limits.

Bernanke

see i cannot tell... I have read numerous posts that "claims" computer will freak out. benz diffs don't have a electrical plug in them to tell the computer which ratio is in the differential so it makes sense that it would freak out but i've never actually heard of a case where it actually happened. I would hope it was all just forum myth/rumor.

Bernanke

ya i hear you. Benz gearing is SOOOO rediculously long, you don't need more power in any AMG, u just need better gearing. gearing alone will take serious time off your 0-60 and 1/4 miles especially if its Limited Slip. 2.65 is a rediculously low gear. W210 E55's have 2.82s and I plan on upgrading to 3.27 gears from a E320 diff and just put a limited slip style unit in there (maybe phantom grip, depending). 3.27 gears would give the car a 16% increase in mechanical torque and if you can get sticky tires and LSD to put all that extra torque to the ground thats a substantial difference in acceleration, it shouldn't be much slower than a stock W211 E55. anyways thats why i want to find out exactly if its for sure necessary or not, b/c if not then i can just put the diff in and not worry about it. diff and LSD alone shouldn't cost more than $800 tops.

Bernanke

Directly off MKB website ...

" The combination of mechanically strengthened MKB transmission and the electronic control unit creates a completely new feeling when you drive. Engine and transmission are tuned together harmoniously to ensure you glide smoothly or to allow you fast, accurate gear changing and a secure feeling when you wish to get the most out of your car: safety that feels right and lasts.

The increased performance means higher strain on the differential. We offer a number of solutions. Mechanical MKB self-locking differentials provide more traction, different axle transmission ratios for more top speed, more acceleration or more relaxation – just as you wish."

and also under E55 section...
" Automatic transmission enforcement incl. Adaption of EGS MKB 27008
transmission ratios i = 3,06 35002100306
transmission ratios i = ? incl. Limited slip differential
differential limited slip differntial 45% 35001700327"

to me it sounds like the adaption of EGS is apart of the automatic transmission re-enforcement mod more than the actual differential, is that just me or not?

Bernanke

SL65 also has a electronically controlled clutch based limited slip differential (i believe) though so thats also another issue, the software may be needed b/c of the complexity of the SL65 diff. themore research i do the more it shows that the software is to improve the transmission itself and nowhere does it say anything about EGS having gearing programed into it...

directly off renntechs website...
"RENNtech offers a multitude of driveline performance upgrades. Upgraded driveline components are often overlooked but can be essential to reliably putting all those additional horses to the pavement. Transmission durability and performance can be improved by increasing the number of and strength of clutch plates, additional transmission cooling, or software upgrades to reduce shift time and alter shift points. RENNtech also offers upgraded constant velocity joints and drive shafts to further strengthen the driveline. Please contact a RENNtech sales representative to learn more about the transmission upgrades available for your Mercedes"

that also makes it sound like the software upgrade is for the reduced shift time and alter shift points (like most auto software upgrades, dinan has an idential thing for BMWs, i did it on my auto M3 when it was auto).