O.K., fine, but while we're kissing his bottom, will his top end be affected - or will it be as fast, or faster?

HAHAHAHAHA... That's right, you both will be KISSING my ass after I beat the two of you. :devil:

Anyhow, as a result of changing my gearing to a higher number my top end will be affected negatively. Not really too worried. All that matters is I'll be putting down some serious torque down low.

Yeah, I guess most of the racing is done off-the-line and in lower gears....can't wait to see the mod when it happens! VT you should be the one going for the full R54 conversion!

Seriously affected! And consumption too . But great acceleration .
At 145 kmh (90 mph) he will have 3800 rpm instead of 3000 .

I think he'd be alright with a 4.10 final drive, especially if acceleration is the goal. 4.10s might be a bit of a hassle with a traditional manual, but with SMG, it shouldn't pose a problem.

If you're considering a supercharger in the future however, I'd definitely look into other gears.

Compared to a stock 545i, VT with gears will reach the speed limiter of 155 in a shorter time. Sure, he'll have a lower theoretical top speed, but with an electronically limited speed to begin with, it doesn't really matter. Loss of top speed shouldn't be an issue unless you're on the unrestricted portion of the autobahn.

You will have better gas mileage than him though :thumbsup:

I spoke with my dealer the other day about swapping out ring and pinions, dinan rear diff and other options. I also did some parts research and this is how things are summarized at the moment.

BMW says that they do not swap ring and pinion gears. They swap out the entire diff as a single unit, everything but the cover and the fluid. The gears in a 550i Step are 3.38 compared to manual 2.93. The driveshaft on the Step is 2mm shorter than the manual/SMG, but Tech said they could make it work. The problem is, I was told if anything ever went wrong with the drive train the first thing they will try to do is point at the incorrect diff in the car as the culprit. Even though it is a BMW part installed by BMW techs. He indicated the safe way was the Dinan, but the difference in diff cost is $500 versus BMW diff. I was told no warranty issues with Dinan diff, funny huh, aftermarket trumps OEM.

I too want shorter gears in my manual 550i and it will be the first major mod I undertake. He also told me that the dealership may be having a Dinan day soon where they will discount parts/labor. I think I will wait and see.

I will check into the RD Sports ring and pinion gears to see how feasible the swap is. Vegas, keep us informed of your pioneering progress.

al

Hi Everybody! I'm jumping in late on this thread. Great stuff. Some of you guys are true gearheads. ;-)

I would appreciate if somebody could help me here. Maybe a brief synopsis of what is available *potentially* for me.

I have a Brand New 08 550i Steptronic with Sport Package(loaded--minus active steering).

Is there any benefit for me to change the differential when my car is already a steptronic?

Knowing this car is really quick and possibly quicker than the 360hp claimed------what kind of gains would I realize---HP and Low End Torque?

I appreciate the info.

SoCal

To gain 30 HP you have to replace the stock exhaust with a custom exhaust like mine .
Search for my exhaust thread with pics .
After catalysts with 100 cells .
And finally map .
I think at least 50 HP with his 3 mods .

I will go with 3.23 .


Wonderful final drive ratio!!!