diff help needed

[groovylee]

hi all,

i have been thinking about tidying up the diff on my car when i do a few other bits back there, but have seen a 3.91 320i auto open diff for sale, which i could refurb and swap over with mine. the trouble is, i'm not sure what mine has on it already?? or if this would mess things up?

the car is a 1990 320i auto cab.

any thoughts?

many thanks,

Lee

[Grrrmachine]

According to the Wiki - http://www.e30zone.net/e30zonewiki/inde ... ferentials

you'll have a 4.27 most likely, so a 3.91 will make the car feel pretty sluggish.

[mrLEE30]

Look at the small metal tag affixed to one of the diff rear cover bolts, what do the numbers say? Helps to spray it with WD40 and brush with a Brillo pad if you can't read it.

[groovylee]

cheers guys, i will have a closer look at mine later.

grrrrmachine: would it mean longer gears? i.e less acceleration, more top end? not too hot on gearing figures

[randomspeedfreak]

cheers guys, i will have a closer look at mine later.

grrrrmachine: would it mean longer gears? i.e less acceleration, more top end? not too hot on gearing figures

yes, a lower ratio on the back will have this effect

[Grrrmachine]

Taken from that exact wiki article:

"The ratio will affect the performance characteristics of the car. A shorter gearing (larger number) will make the car accelerate faster. By contrast, a longer gearing (smaller number) will accelerate slower for any given gear. The other thing to remember is that shorter gearing will mean higher engine revs for any given speed and longer gearing will mean lower revs for the same speed."

Have a read of the article; I didn't understand diffs either until I read it, and it all makes sense to me now

[daimlerman]

Lift both rear wheels clear of the ground and mark the inner edge of one tyre(a strip of masking tape will do)then turn the prop and count how many turns of the prop to one turn of the wheel.Not as accurate as reading the diff tab,but when the diff tab is so rusty it is illegable,it will give you an idea of the ratio.

[groovylee]

cheers gents. i finish nights soon, so will have a good butchers, but it sounds like it's a no go idea anyway as the sluggish feel is not what i'm after, it is a slushbox already, doesn't need to be any slower