Final drive gearing

Thinking of going the diff change route on my CSi sometime in the future.

Have read previous threads and seems can choose from E32 740 or 750, or E34 M5 or 4litre V8 to get a LSD in the right size to fit the 8.

Have tried searching around to find what final drive gear ratios are available in those models, but having difficulty.

Anybody help out with ratios available ?

Also anybody with some advice on what ratio might suit CSi (manual box) to improve acceleration but without getting too manic on the gearchanges (still like to get 60 in 2nd).
Not bothered about fuel consumption. Would sacrifice some top speed, but would be nice if it could still make it to 155.
Have seen 3.91 (too manic for the CSi?) and 3.64 mentioned and notice Faisal has 3.15 in his 860 manual.

Schnitz,
Thanks.
Silly of me, looked at e31 site yesterday and missed the obvious (getting a diff from an 8 series, rather than another model)

Of ones that would be some use to me looks like the 3.15 from the Euro 5 speed auto 850i or the 3.64 from the US 5 speed auto 850i.
Outside of the US, later 850i is fairly rare. Doubtful if I could find one in UK ?
(talking about the 3.64, realise you have the 3.15)

Question is - do they have LSD ?
(would still like to have that as per CSi)

Thanks for the offer of the 3.15. If it has LSD, might well be interested if overall gearing is suitable.
Will soon try downloading the gearing calculator on the "gearboxman" site to check that out.

Thanks Seb,
Using that calculator, gives me plenty of choice of ratios.
Just depends on how much gear-changing I want !

Using 6000rpm as change point (bit high maybe)
Even 3.91 gives 142mph max in 6th
3.64 goes over 150mph.
All the so far suggested ratios (3.91, 3.64, 3.15) need to be in 3rd to make it past 60mph (compared to 2nd with standard 2.93 gearing).

Thinking of 1/4 mile times, 100mph(ish) comes up in 4th or 5th gear, compared to 4th with standard gearing.
So not a lot of difference there.

So back to the original question - suitable LSD gear ratios available from which car source ?

Thanks guys,

Are the ratios marked on the outside of the casing or tag anywhere ?
Seems 740s and 750s are more common in the breakers, 540s also.
Would be useful to know their ratios.

Faisal,
Is your 3.15 with LSD ? If not, any problems ?

Thanks for the info,
Started searching on ratios again. I'm sure I'll find some conflicting info but ....

bmwmregistry (reliable?) lists E34 M5 ratios as:-
3.91 - cars built before May '94 EXCEPT
3.73 - US cars with '92/3 model year spec
3.23 - cars built after May '94 (only about one year production)
All LSD, all with 25% lock-up.

Only thing I've found so far on other models is E32 750 with 3.15 (LSD?)
740 nothing so far
E34 540 nothing so far

Tony,
Yeh, 3.91 I think is going to be too much.
Presently thinking of 3.64 or lower.

Off the line, the CSi with standard gearing, already needs some pretty quick shifting into 2nd and 3rd.
Only makes it just to 60 in 2nd.

From 3rd onwards, the shifting slows down with standard gearing.
On quarter mile, seems to lose momentum in 3rd and you are only just in 4th crossing the line.

With the change in gearing, aim is to get all that weight off the line a little quicker (they say more time is lost in the first few feet than anywhere else) and then improve acceleration through 3rd/4th.
With lower gearing, theres only maybe one gearchange difference to 100ish compared to standard, just (as Faisal says) got to be quick on the changes in the lower gears.

BTW did I see in one thread that you are a Blackpool boy ??

Tony,
No, based in Norfolk for a long time now (and not even there much - work abroad).
However, spent most of my early life in Backpool area and most of my family are still there.
Try to get up to see me Mum (in Cleveleys) when I'm back, every few months. Was up in Sept and first time in the 8.
Best (& fastest) drive I've ever had to there !
(you ever had this problem in the 8 ? Everybody wants to race ?!!)

Anyway - back to gearing .........

Peter,
Is that with the engine/gearbox cold, or all the time ?

I have the same problem (and so do most other people with manuals it seems) when cold and I have to take it slow to get 2nd to slot in.
However, after a few miles (and doesn't take long) 2nd is fine and is as quick into place as the other gears.
Once warmed up, have never had a problem hitting second even on repeated drag-strip runs.
Funny thing was, found I was missing 4th on a number of runs - never happens on the road ....??

If having the problem continually, maybe look to the clutch/slave cylinder ?
Changed mine recently, and improved matters when cold.
The gearboxes themselves are supposed to be very strong, don't often hear of problems.

Extra gear changing - don't see it as that much of an issue. In normal road driving around town, I tend to go up through the gears fairly quick anway, get in a comfortable high gear to save a bit of fuel.
If really "trying" on road or track, would only be (maybe) one extra gearchange to 100mphish.....
I enjoy gear-crunching anyway, but that's just me ...

Steve,
Yeh, perhaps I should have been a bit more specific...
Most (not all) proper performance cars (drivers), I've found seem to have some respect for the car - even admiration.

Normal(ish) cars - different matter .....
I've had 4x4 SUvs, local taxis, standard Fiestas, you name it, trying to beat the car away from the lights.. or pulling away from roundabouts.
Open road/motorway - same again, certain drivers seem to see the car and have to get in front of it (no matter what the speed) ! Particular culprits - the usual quick turbo-diesels - what is it about 5 series diesel drivers ?!

Just my experience ......