Rear end build advice - Page 2

SkipB · #21 (**permalink**) 01-25-2007, 05:22 PM

Heys Guys,

Go to the www.diffsonline.com that Whiplash recommended. They have a great gear/speed ratio chart that you can plug in your tire size, rear end ratio, gear ratios and it calculates speed in each gear. Pretty neat.

SkipB

JayBar · #22 (**permalink**) 01-25-2007, 06:58 PM

Also check out http://www.5speedtransmissions.com/gear_calculator.html
already has the gear ratio's for various transmission.

Cobra75 · #23 (**permalink**) 02-21-2007, 06:25 AM

Can anyone explain the % lock on the BMW differentials?

Does it mean the diff locks up when the % difference between the two rear wheels rotation is met? i.e. at 40%, the diff locks when one wheel is spinning 40% more than the other.

Or does it mean the % torque applied to the spinning wheel?

jeffko · #24 (**permalink**) 02-22-2007, 07:31 PM

It is the percentage of slip (as torque is applied) that the diff will allow slip. The greater the percentage the quicker the lockup reacts.

Cobra75 · #25 (**permalink**) 02-22-2007, 08:17 PM

Quote:

Originally Posted by jeffko

It is the percentage of slip (as torque is applied) that the diff will allow slip. The greater the percentage the quicker the lockup reacts.

???????????????

I apologize, for being confused here. I read your response over and over, but it appears to me that your two statments contradict each other.

1. "It is the % of slip the diff. allows." Therefore, the higher the %, the greater amount of slip allowed. Or a 40% diff allows more slip than a 10%.

2. "The greater the % the quicker the lockup" Therefore, if it locks up quicker then it follows that less slip is allowed. Or a 40% diff locks up quicker (less slip) than a 10% diff.

Which is it?

Gun Doc · #26 (**permalink**) 02-22-2007, 10:51 PM

Cobra 75,

The percentage number in an LSD refers to the amount of torque applied from the faster (slipping) wheel to the slower (wheel with traction) thereby limiting slip. The higher the percentage, the more tire wear you will see on the inside wheel during cornering, because the tire will slip as it attempts to counteract the LSD's tendency to drive both wheels at the same speed. Higher percentages also increase over steer in slippery conditions and under steer in dry (good traction) conditions. Of course for straight-line acceleration a higher number puts more horsepower to the pavement.

Gun Doc

Cobra75 · #27 (**permalink**) 02-23-2007, 05:14 AM

Ah...now I get it.
Thanks Doc.

jeffko · #28 (**permalink**) 02-23-2007, 03:32 PM

I guess it should have read "It is the percentage of slip (as torque is applied) that the diff will NOT allow slip. The greater the percentage the quicker the lockup reacts.