brandsb

I've been searching but haven't found a difinitive answer. Previous rear gear changes such as Dinan don't work with Steptronic E60's. When I previously researched this it was due to the electronics link to the transmission.

I'm most interested in the option to change rear end gear ratios with a LSD....will the Quaife system allow for that with the Step? Also, who's the best source for technical info regarding Quaife?

AlexFW

Quaife would be ok almost 100% sure. About ratio.. diffsonline.com and other said you cannot change ratio on the step.
But .. On the step you already have 3.38, with a 60mph 2nd gear.. Why more acceleration than so ?

mhs525

I have the Quaife LSD and was told no on the ratio change by TMS and Diffsonline.

Dinan does offer a ratio change for the manual and SMG but not steptronic. No tuner has better access to BMW information than Dinan so there must be a reason they don't offer it.

IMO the Quaife is still a great mod without a ratio change. The car feels a lot faster off the line because it's putting down the power vs. the having the electronics kick in to control wheel spin. I have 18x10 BBS rear wheels with Michelin Pilots and the car launches hard with the LSD. It pins you back in the seat.

brandsb

You're joking, right?

Seriously, one more ratio would definitely be nice but it doesn't sound like it's in the cards.

brandsb

I also spoke to Diffsonline but it was a couple of years ago. At the time they checked with Dinan and told me that the electronics in the feedback loop to the Steptronic were too complex for a gear change. I was hoping that the Quaife system had overcome this but apparently not. I do take your point regarding the LSD though.

silvergray5456spd

how much does the Quaife LSD run and where do you get it?

mhs525

Mine cost $2,700 installed. The labor is expensive. The rear end has to be pulled from the car and rebuilt installing the Quaife unit then reinstalled in the car. TMS and difffsonline did mine. You need someone qualified to do this. Rear ends need to be set up just right or bad things happen.

tbal

having the lsd... does it just feel different, or would say for dyno sake, would it make a difference in rwhp??

mhs525

There is no change in rwhp. The car does not make any more power. The LSD allows you to use the power the car is making.

For example if you are trying to pull onto a busy street, you car has 300 ft/lbs of tourqe. You hit the gas but the rear wheel loses traction and the traction control kicks in, brakes the wheel and cuts power to control wheel spin. You are not getting 300ft/lbs of tourque becasue the computers are cutting it back to control wheel spin. With the LSD, and good tires, both tires get power, less wheel spin, car pulls out faster.

I never thought an LSD was a big deal until I had an M3. My 545i just didn't feel like a BMW until I installed the LSD. The only reason all BMW's don't have them anymore is because of cost and to make the M cars feel special. 335/535/550 have so much power who needs an M car???

You really need to drive an LSD equiped car back to back with a "peg leg" diff to feel the difference.

I will always upgrade to LSD's in my cars...

Rizbel

Is it possible to replace 545/550 std diff with an M5/M6 LSD? Even in a steptronic? Thanks.