Limited slip differential

[drum2430]

Hey Guys,

I have the opportunity to buy a 4:10 lsd and I am thinking about putting it in my '90 535 ( automatic tranny ). The current lsd is a 3:65 ( or so ). I know the car will probably be a real neck snapper off the line but I am concerned about how much the cruising capabilities of the car will suffer? Will I see something crazy like 4000 rpm at 70mph? Are there other considerations that have to be addressed when making this conversion? I am hoping the considerable wealth of your cummulative experience will provide what I need to make an intelligent decision.

Thanks in advance.

Gordo.

[Kalevera]

Check KMS's site on this (http://www.koalamotorsport.com). Brett's got a good article on the diffs of diffs. I was doing the exact same calculations on my car last night.

My '90 535iA has a 3.91 LSD (cold weather package). At ~ 70mph, I run about 2900 RPM. If I put in a 4.10, I go up about 300 revs, to about 3200.

Not that bad, but I'd rather just keep the current gearing and save the money on gas.

Best, whit

[billy in slo]

You should have a 3.91 in your 90 535iA. I am going with a 4.27 lsd in my 90 535iA and I don't think it will be anything close to "a real neck slapper" after the swap. I am hoping it won't be as much of a lard arse off the line that it is now. As for the revs at cruising, remember these cars were designed to cruise at 100 mph + so while it will be turning a little faster it won't be unacceptable. Good luck.

[632 Regal]

multiply your rpms at any speed by 1.126 and see what the rpms will be with the 4:10.

[632 Regal]

be about 4500 at 100 mph according to Dereks sig pic.

[bahnstormer]

i went on my 90 535i auto
from 3.91 to 4.27....this car
is chipped...

some difference, but not much around town
highway is just some more revs
used to be 3 grand 80mph now its like 3300 or so?

[niall]

here is the easiest way mate, use this gear ratio calculator. http://www.unixnerd.demon.co.uk/revs.html