BMW Motorsports Final Drive

[2K11SGCoupe]

Originally Posted by Mike Benvo

Careful when going with an aggressive ratio on a DCT car, you can cause all sorts of shifting funkiness.

Mike which final drive ratio do you have in the e92 with the Harrop supercharger? If someone was planning to eventually install the Harrop unit on a DCT e92 M3 would you advise keeping the 3.15 or going to 3:45 gear set.

Thanks -

[BPMSport]

Originally Posted by 2K11SGCoupe

Mike which final drive ratio do you have in the e92 with the Harrop supercharger? If someone was planning to eventually install the Harrop unit on a DCT e92 M3 would you advise keeping the 3.15 or going to 3:45 gear set.

Thanks -

I have the stock 6MT diff in my car.

I would probably advise to stick with stock gearing in this case as 1st, 2nd, and 3rd gear would probably be useless with a more aggressive ratio.

Originally Posted by Redd

The consensus is that it's not recommended to run 3.62 in DCT due to issues with rev matching and possibility of mechanical over rev.

Mechanical over-rev is not an issue. It will cause other quirky DCT operation - not just rev matching issues.

[DavidZ]

Originally Posted by driftflo

i currently have the following parts in stock:

- 4.44 new
- 4.10 new
- 3.91 new & used
- 3.85 new & used
- 3.73 used
- 3.64 used
- 3.62 new & used
- 3.45 used
- 3.25 bmw oe new
- 3.23 used

all new gearsets are original bmw motorsports parts (except 3.25, this is an non-ms bmw part).
only the 4.10 and 4.44 feature a shotpeened surface, the others are more or less the same than the non-ms parts!
bmw gearsets are of very high quality and still quite affordable (compared to i.e. porsche gearset prices). aftermarket stuff is more expensive and often fails so i always try to usw oe parts here.

Do all of these ring gears require a different pinion gear (from the stock-installed)? What about the 4.10 specifically?

[///Mobbin]

Do our cars keep track of over-revs like Porsche's do?

[BPMSport]

Originally Posted by ///Mobbin

Do our cars keep track of over-revs like Porsche's do?

Absolutely.

[Rajmun340]

Originally Posted by ///Mobbin

Do our cars keep track of over-revs like Porsche's do?

Does accelerating in 2nd and forgetting to upshift to 3rd before hitting the rev limiter drop the RPM automatically constitute an over-rev that the car keep track of ? Or is it only downshift over-revs that count ?

sorry for the slightly off topic question, always wanted to know this.

[///Mobbin]

Originally Posted by JoeM3SSII

Does accelerating in 2nd and forgetting to upshift to 3rd before hitting the rev limiter drop the RPM automatically constitute an over-rev that the car keep track of ? Or is it only downshift over-revs that count ?

sorry for the slightly off topic question, always wanted to know this.

Looks like both are logged, see Dave's explanation below.

[///Mobbin]

Originally Posted by Mike Benvo

Absolutely.

Good to know, thanks. What do you need to check this? Also, are they logged the same on 6MT and DCT cars?

[driftflo]

Originally Posted by DavidZ

Do all of these ring gears require a different pinion gear (from the stock-installed)? What about the 4.10 specifically?

yes! even changing to another gearset of the same ratio requires changing both, ring and pinion. they are paired and always belong together!

[Dave07997S]

Originally Posted by JoeM3SSII

Does accelerating in 2nd and forgetting to upshift to 3rd before hitting the rev limiter drop the RPM automatically constitute an over-rev that the car keep track of ? Or is it only downshift over-revs that count ?

sorry for the slightly off topic question, always wanted to know this.

Max rpm is always recorded...whether its a mechanical over-rev or momentum from accelerating. Even though the car has a fuel shut off at 8400rpm, it can go above that through momentum during acceleration, as the car revs so fast.

Dave

[Dave07997S]

For those of you who are thinking of doing this, such as myself. You have to have the backlash and pinion depth adjusted perfectly or you will destroy the gears and get a nice whine. I know a lot of good shops that won't touch a R&P install.

Dave

[///Mobbin]

Originally Posted by Dave07997S

Max rpm is always recorded...whether its a mechanical over-rev or momentum from accelerating. Even though the car has a fuel shut off at 8400rpm, it can go above that through momentum during acceleration, as the car revs so fast.

Dave

Interesting, I assumed the fuel shut off would cut off the potential over-revs in a predictable way that didn't need to be logged, makes sense to just log all over-revs though.

[///Mobbin]

Originally Posted by driftflo

if you get the right software, there are no issues with the 3.62 gearset.
if you dont change the software there may be issues in automatic mode indeed.

what you also should keep in mind: the 3.45 gearset can be installed without changing the rear differential cover! for the 3.62 you will need the cover from a 6mt car!

A few months back I got the GTS DCT software flashed on my car (DCT w/ 3.45 diff). After substantial street time and a few track outings I'm not sure it's a perfect match with this diff. The shifts are insanely fast when in S4/S5/S6 but the rev matches seem less precise now and I still get transmission lurch at slow speeds, especially in D mode (when stopping and going). No true functional issues, just not sure my system is working well with this setup. Thinking to go back to non-GTS DCT software.

Any thoughts before I make the switch back?

[bigjae1976]

Dumb question...is a 210mm R&P universal among all BMWs that us a 210mm case? So can I use a 3.62 from an E46 M3 in an E90 M3 DCT?

[Richbot]

I believe that's where some of these ratios come from yes; just slightly different back covers for different apps

<- hurr internet expert durr

[lutfy]

Originally Posted by ///Mobbin

A few months back I got the GTS DCT software flashed on my car (DCT w/ 3.45 diff). After substantial street time and a few track outings I'm not sure it's a perfect match with this diff. The shifts are insanely fast when in S4/S5/S6 but the rev matches seem less precise now and I still get transmission lurch at slow speeds, especially in D mode (when stopping and going). No true functional issues, just not sure my system is working well with this setup. Thinking to go back to non-GTS DCT software.

Any thoughts before I make the switch back?

Exact same observation. The shifts are too jerky for street driving and on track, high rpm shifts one can hardly tell/notice. Partial WOT or 5-6k shifts on the street is a nuisance (fells like I will kill the clutch this way). If I knew before, I would be keeping non GTS tune myself.

On the track, the stock ratios are fine too (both short and long); at least for me.

Lutfy

[Hujan]

Originally Posted by lutfy

Exact same observation. The shifts are too jerky for street driving and on track, high rpm shifts one can hardly tell/notice. Partial WOT or 5-6k shifts on the street is a nuisance (fells like I will kill the clutch this way). If I knew before, I would be keeping non GTS tune myself.

On the track, the stock ratios are fine too (both short and long); at least for me.

Lutfy

Are you on the stock diff?

[lutfy]

Originally Posted by Hujan

Are you on the stock diff?

Stock diff indeed. Also from what I gathered, GTS has a transmission cooler unlike non GTS. Its more for laptimes vs durability (cant wear out my clutch too fast...)

Lutfy

[///Mobbin]

Originally Posted by ///Mobbin

A few months back I got the GTS DCT software flashed on my car (DCT w/ 3.45 diff). After substantial street time and a few track outings I'm not sure it's a perfect match with this diff. The shifts are insanely fast when in S4/S5/S6 but the rev matches seem less precise now and I still get transmission lurch at slow speeds, especially in D mode (when stopping and going). No true functional issues, just not sure my system is working well with this setup. Thinking to go back to non-GTS DCT software.

Any thoughts before I make the switch back?

Originally Posted by lutfy

Exact same observation. The shifts are too jerky for street driving and on track, high rpm shifts one can hardly tell/notice. Partial WOT or 5-6k shifts on the street is a nuisance (fells like I will kill the clutch this way). If I knew before, I would be keeping non GTS tune myself.

On the track, the stock ratios are fine too (both short and long); at least for me.

Lutfy

FWIW, with the GTS tune I've found that running in the lowest throttle response setting (ie. Power button off) and D3/D4 reduces transmission lurch when stopping/starting. Still though, I agree about the high speed shift benefits being more of a nuisance on the street and the rev matching is off as I mentioned before, at least in my car and especially in the more aggressive throttle response settings (Power and Sport Plus).

I still plan to switch back to the latest BMW non-GTS program soon. And S5 or S6 with the standard program are both fantastic and smooth at the track from my experience (in my car).

Anyway, not a huge deal but good info for those considering the switch.

[srmast1]

I was looking into going from a 3.85 to a 4.1 in my 6mt e90. That's roughly a 7% increase in torque to the wheels. Is that something I would even notice? Is there any real point in going from 3.85 to 4.1, acceleration/performance-wise?

[bigjae1976]

Originally Posted by srmast1

I was looking into going from a 3.85 to a 4.1 in my 6mt e90. That's roughly a 7% increase in torque to the wheels. Is that something I would even notice? Is there any real point in going from 3.85 to 4.1, acceleration/performance-wise?

You'd notice it but it won't be mind blowing.

[srmast1]

Originally Posted by bigjae1976

You'd notice it but it won't be mind blowing.

So then probably not worth the 2 grand or so this is bound to cost? I'm just trying to figure out if this is a worthwhile mod or not.