is it true?

[new2bmw]

ok, i am fixing a 91 318i 4 door manual tranny. I am trying to pick the best diff for the car, not for highway but for quick sprints. I have the stock diff thats on the 91 318i, i have a diff from an 84 318i manual tranny and another but this one has me the most confused, a diff from my parts car, a 1984 318i auto, i looked on real oem and it says its a 3.91 25% limited slip? any idea if its true and if so is it open or closed? Which diff would be the most likely to help me get from light to light the fastest? the 84 was manufactured in nov. 1983. i am not sure about the ratios on the other two, maybe you can help me out. thanks guys

[markseven]

4:10 lsd

[325ix]

I think the ix was the only diff offered in a 3.91 but, I may be wrong. Anyways, I would look for a 4.10 or higher.

[mcgillaguddy]

touring was offered in 3.91 as well... found from quick search
Here is a link to e30 diff ratios:
http://www.e30tech.com/forum/showthread.php?t=1863

[dashboardmonkey]

Early 318 came with 3.91 from the factory. If i were you i would find a diff out of a 318ti e36 auto. 4.27:1 ratio

[new2bmw]

lsd

went to real oem and it says my 84 318i (build 11/83) has an 3.91 LSD can anyone verify and if so would that not be kick ass? i am new to this lol. here is the links

http://www.realoem.com/bmw/partxref.do?part=33141210493&showus=1&showeur=&series=E30

http://realoem.com/bmw/showparts.do?model=1084&mospid=47302&btnr=33_0014&hg=33&fg=05

and from the link given by mcgillaguddy the diff in the 91 i am fixing up is a 4.10? This is confusing as i keep looking at different sites and numbers are all different.

[325ix]

Crawl under your car, there should be a little metal tag that tells you, unless it has been ripped off or rusted off.

[new2bmw]

tags

ya i always get the shit, no tag, others too rusty to figure out.

[ELVA164]

The early 318's and later 318's have different engines and different options for differentials.

[new2bmw]

I know

ty if i did not know that would have been great ty for helping. I have both the 84 m10 318i and the 91 m42 318i here so i figured the 84 is too rusted so i am trying to salvage the best parts and any crossover parts so i can have the best 91 318i possible with what i have

[irish44j]

Early 318 came with 3.91 from the factory. If i were you i would find a diff out of a 318ti e36 auto. 4.27:1 ratio

correct. My 5MT 1985 318i has an original 3.91 LSD in it. Still works great 27 years later :grin:

[jeffnhiscars]

I hate to disagree...ok no I dont. According to the owners manual that came with my 84 318i the auto trans came with a 3.46 open and the manual came with a 3.64. Mine started as an auto and has a 3.46 tag on the the diff.

[Red46]

If you want to know for sure...
-pull the cover
-count the teeth on the ring gear
-count the teeth on pinion gear
-divide ring gear teeth by pinion gear teeth

[jeffnhiscars]

So I'm going to have to disagree again, only this time with myself. I had the 318 on the lift the other day and the tag says 3.64. I had the numbers swapped. My bad !

[Smelser]

I have a 4.44 LSD for sale! small case, would be a direct fit!