what sort of super mad ratio is this diff

[craigieeb]

iv just found a diff in my cupboard, it has no tag on it, so i rotated the input shaft, and it rotated the out put shaft once to EXACTLY 3 and a half turn's....???

anybody shed any light on this? i cant remember whether it came from a 320 or a 325i, (im sure it was a 325i) but i know the car was brought over from germany, a few years ago, so what sort of ratio could it be?

ta

(small case)

[kam-325i]

3.50:1 ?

[craigieeb]

bit of a strange ratio dont you think? i'v never heard of a 3.50:1 diff before
and how so i tell if it's an open or a slipper??
i think im having a "blond" day

[kam-325i]

I've heard of a 2.93/4:1 ratio for an E30.
To check if its a slipper, give it me !!!!

Turn one of the output shafts with the input shaft locked(so it does not turn), if the other output shaft turns the same way, its a LSD, if it turns in the opposite direction, then its a standard diff.

[Project_E30]

I have a spare 3.64 or 3.46 cant remember which is not far off 3.5 so sounds like you have the same.

[Jhonno]

sounds like a 3.46:1 diff

both outputs will turn the same way if its an LSD

[craigieeb]

so what would that do on a 325, super speedy gearing but no top end? or just turn it in to a slug, and get 2000000 miles off Ԛ£10's worth of petrol

[billgatese30]

Slug...for super speedy you need a higher number, the lower the slower...gettit

[craigieeb]

gotit

[Jhonno]

erm i run a 3.25 on my 316i Auto which had a 4.45 originally and other than a slower take off its fine on the move would notice it less with a manual imo

small case wont put up with a 325i tho - it'll lunch itself soon enough

[kam-325i]

so whats the "ideal" diff ratio for an every day, standard daily driver 325i ?

[Simon]

so whats the "ideal" diff ratio for an every day, standard daily driver 325i ?

3.64

[Dan318-is]

i thought it was 3.91?

[Simon]

i thought it was 3.91?

I'd much prefer the 3.64, as fitted to early sports, still gives good acceleration, and doesn't run out of steam, just fitted one to the touring, muchos improvement!!

[gcorky]

at 5000rpm in top ,what speed do you do ,im asking because ive just replaced my diff with a unit tagged 3.73(not sure whether its true like)and i show 120mph ,but car seems very low geared!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[Simon]

at 5000rpm in top ,what speed do you do ,im asking because ive just replaced my diff with a unit tagged 3.73(not sure whether its true like)and i show 120mph ,but car seems very low geared!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

If that's aimed at me, I'm not sure yet, as I'm yet to swop the speedo senders over because they were different, diff came from a pre-facelift.

[gcorky]

ello simon no just curious whilst your on ratios ,see what you lot get

[craigieeb]

im prety sure the one i have on is a 4.1 or something to that efect, and flat out in 5th the needle goes past the 150 marker, not sure how accurate it is but it feel's damn fast

(all done on an air strip of course)