Gearing - how low should I go [Archive] - Bimmerfest - BMW Forums

: Gearing - how low should I go

ShifterKart Guy
01-06-2006, 04:45 PM
I am ready to place an order to Quaife for a custom rear diff with 40 % Lock up.........
I have a 2000 M Coupe with a Twin Screw SC.......something has to be done and done today. I am writing on the M forum because there are more fellow M drivers with highly modified E 36 chassis than M Z3's.

The big question that I am wrestling with is what ratio????

Car has stock 3.23. With the Twin Screw,,,,,,,,1,2 and 3 are way short. Fifth is also annoying on the Highway.hitting close to what.........3000 RPMS at 65 MPH

I have used the RPM tool.........most interesting thing is to see what effect Plus 1 and 2 size tires have on gearing and wheell speed!

Doing to 3.15 seems like too small a jump to me.,,,buy going from 17's to 18's I am right back where I would have started witha 3.15.

The AA Tuning cars all run those cars have a ton of RWHP.............something like 600 i can see the need.

I am looking for comments and feedback.........throw it out there if it adds value to the thread...........

I am leaning toward a 2.90 to 3.00 custom quaife diff.

My objectives are:

1) To be able to use the low end torgue of the Twin Screw
2) To drop highway RPM's in fifth
3) Reduce throws from zero to 100
4) Improve higher end to 60 is less important to me than 40 to 140

Anyone have any experience with longer diff ratio for 5 speed...keep in mind car puts out over 350 rwhp ..and over 285 ft lbs of torgue with most of it as low as 2500 rpm's.

Thanks for reading and your comments.... :thumbup:

01-07-2006, 07:44 AM
A 2.93 is your best bet. There are issues with a Quaife that you should understand. I would talk to Dan the owner/operator at for specifics. A totally rebuilt diff with 40% lock up, no quaife, is like $1400 plus core. Dan is a great guy and is highly recommended.

ShifterKart Guy
01-07-2006, 03:26 PM
Thaks_ emailed him last night to see what he has to say......

I am not committed to Quaife...its just a name to me with good brand recognition.

End of the day.....I want soemthing that works and is not going to blow up or be noisy two weeks after install.