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View Full Version : Help figure out what diff ratio I have


permit
02-06-2006, 03:14 AM
Alright, I have a 1990 535i 5-speed and I just got under the car for the first time only to see a big "S" on the bottom of the diff. I was always under the impression that it was an open diff (I think I searched what the stock 535 diff was, can't remember it though), so now I'm left wondering what ratio mine is.

At 3k rpms, I'm going 80mph in 5th gear. That's about all I can give you.

Anyone have a guess as to what it is? I'd rather not be told to get under the car and check out numbers on the side of the diff.
Paul in NZ
02-06-2006, 03:19 AM
I have a 3.64 and at 100 k which is 62 mph i am doing 2300,so for each 1000 rpm i do 26.95 so 3000 rpm =80.86....guess what ratio you have
rob101
02-06-2006, 03:38 AM
I have a 3.64 and at 100 k which is 62 mph i am doing 2300,so for each 1000 rpm i do 26.95 so 3000 rpm =80.86....guess what ratio you have
what kind of tyres do you have?
and what's the Gearbox overdrive ratio?
Paul in NZ
02-06-2006, 03:48 AM
Sheesh
I run 235 45 x 17 tyres,and my top gear 260/6 getrag ratio is 0.81 according to gales page.I beleive one of the sport options is a slightly lower diff ratio than the normal 3.46 535
permit
02-06-2006, 04:00 AM
Oh, and I have 245/45 & 265/35/18s. It's off by such a small amount that it shouldn't matter in this situation. 3.64 sounds right.
ILoveMPower
02-06-2006, 10:56 AM
I have 3.64 on stock basketweaves... 3rd gear, 3000rpms = ~80mph
RobPatt
02-06-2006, 12:55 PM
... don't know what diff that is, but would have thought it'd be different than 535i w/gertrags and a 5 speed tranny (verses my 4 speed auto GM). ?
Rigmaster
02-06-2006, 01:31 PM
535i 5 speed should be a 3.46:1 ratio.

LSD was an option- it's hard to tell which cars have it and which cars don't without a visual check of the diff or the tag.


Bret
permit
02-06-2006, 02:20 PM
It's not too hard to tell if it's an LSD. There's a giant yellow "S" on the bottom of limited slip diffs.
Rigmaster
02-06-2006, 08:01 PM
It's not too hard to tell if it's an LSD. There's a giant yellow "S" on the bottom of limited slip diffs.


What I said was it's hard to tell if the car has LSD "without a visual check of the diff or the tag". The "S" is white, there's supposed to be one on the bottom, and usually one on the top- but that one's hard to see unless the diff is removed from the car.


Easiest way to tell is to scrape the crap off the metal tag and look for the "S" stamped on it.


Bret.