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Ceeker
03-23-2009, 03:49 PM
Got a 90/4 door auto; thinking of swaping in a 87 325is LSD.

Could someone tell me if the ratio's are different or same?

thanks

craz azn
03-23-2009, 03:51 PM
87 iS ratio will be a tad longer. 3.73 VS a 4.10

Ceeker
03-23-2009, 04:16 PM
ah ok..so my current diff is a 3:73 and the IS- 410?
This ideally will give me more off the line right?

Ceeker
03-23-2009, 04:29 PM
sorry...dislexic...(Grin) my car will be a dog with the longer gears..shame..

m60e30
03-24-2009, 12:20 PM
im thinking the 87 is will also be a 3.73

Ceeker
03-24-2009, 01:29 PM
If that is the case, I'd love to know because I'd like a posi in the car. :-)
Would anyone know forsure....?

"k"car man
03-24-2009, 02:06 PM
wouldn't the IS have a standard tranny in it? and between the standard and auto trans arn't the pinion's on the diff different?

Ceeker
03-24-2009, 02:20 PM
all your inputs are appreciated; I need a clear answer however; Would the 325 auto have a taller ratio then the 325is 5 sp standard? I believe the 325is has 3:73 ratio. If someone actually knows for sure I'd greatly appreciate it. I'm too lazy to climb under my cars to actually read the numbers off it.

thx a bunch.

"k"car man
03-24-2009, 02:33 PM
well I took a diff out of a 88 325is and it's the same as my 84 325es there both 3.23 posi ratio so you might be crawling under your car. In my computer system at work it shows a 84 325es to have a 2.93 ratio and a 88 325i to have a 3.73 and a 89 325i to have a 3.91 all 5 speed cars the auto's show a 4.10 ratio

craz azn
03-24-2009, 02:46 PM
all your inputs are appreciated; I need a clear answer however; Would the 325 auto have a taller ratio then the 325is 5 sp standard? I believe the 325is has 3:73 ratio. If someone actually knows for sure I'd greatly appreciate it. I'm too lazy to climb under my cars to actually read the numbers off it.

thx a bunch.

Depends what year Automatic 325i. Later cars cars came with a 4.10. Which is shorter than the 3.73. I think you mixed that terminology up.

well I took a diff out of a 88 325is and it's the same as my 84 325es there both 3.23 posi ratio so you might be crawling under your car. In my computer system at work it shows a 84 325es to have a 2.93 ratio and a 88 325i to have a 3.73 and a 89 325i to have a 3.91 all 5 speed cars the auto's show a 4.10 ratio

No 325i/iS comes with a 3.23 or a 3.91. At least not for the N/A market. All 325i/iS have a 3.73 gear ratio, with the exception of later automatics which had 4.10 gears.

"k"car man
03-24-2009, 03:32 PM
Thats odd, cause I pulled the parts off the car a year ago at a auto wreckers in Oakville and the car was a 88 325is I took the drivers door the head off the 2.5L with computer and a bunch of other stuff. car was hit in the front. I even have the vin off the car. Maybe the old owner put that diff in who knows. My 84 325es has a 3.23 posi in it, I would love to have a 4.10 posi in it or a 3.73 posi.

m60e30
03-24-2009, 03:39 PM
ya those are weird diffs. 88 325is should be 3.73 without a doubt. and 325es had the 2.93 lsd

"k"car man
03-24-2009, 03:51 PM
That is odd, it is stamped in both cases in the top corner.

Ceeker
03-24-2009, 04:31 PM
ok, so the verdict then is my 90/325i auto most likely has 4:10 and the 87/325is has 3:73 which sounds right. Anything lower geared would make the car perform slow. Seeing the car is auto and slower then a standard would make sense to put a taller ratio gearing in to compensate.

thx for everyone's input.

racer-x
03-26-2009, 08:42 AM
Sorry to hijack your thread,
but I am looking for a 3.23 LSD, if anyone happens to have one.

Ceeker
03-26-2009, 09:22 AM
If I crawl under the cars; looking at the backing plate where in relation to this are the stamps?
thx.

craz azn
03-26-2009, 09:41 AM
There is a little tag attached on one of the bolts on the rear cover.