|
In Reply to: 850I rear axil ratios posted by Ken on March 14, 2000 at 13:04:27:
I changed mine from the 2.65 to a 3.15 and will never, repeat never, ever go back. What a kick in the pants! I know its a Grand Tourer, but in my opinion, the car is grossly overgeared for normal use in the US unless you're going to regularly cruise at 140 mph or more.
Changing the 6spd's diff to 3.15 basically converts 6th gear to very nearly the same rpm/ratio as your current 5th (actually 2800rpm at 80mph vs. 2400 for the 2.65). If you can live with your highest available gear having about the same overall ratio of your current 5th, and a decrease in highway mpg, you'll like it. Top speed (sans rev limiter)is about 167 mph instead of the theoretical 180mph.
From a practical standpoint, I've ended up actually using 6th gear, the shift points are tighter, similar to a close ratio box. You find yourself in the torque band more often which means faster acceleration in all gears. I havn't timed it, but I'd conservatively guess the result to be at least a .3 sec faster quarter mile.
You could use the automatic's 3.64, but the first gear ratio would likely mean starting in second gear and top speed drops to something like 137mph. 80mph in 6th would be at approx 3,300 rpm, which is a bit high.
When I changed mine I ended up with a spare 3.15 in the process. I also have a comparison spreadsheet for the 2.65, 2.93, 3.15 and 3.64 by gear/rpm/mph. Email me if you're interested.
© 1997 -
2008
Jump Internet Inc. All rights reserved.
