Final drives - what comes from what?

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blacke30
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Final drives - what comes from what?

Postby blacke30 » Mon Mar 23, 2009 12:34 am

So, I thought I would post something useful for once. This comes from the E30 Restoration Bible. I posted this for the people that don't have the book, and are not sure what their car came with. If you need anything else, let me know and I'll try to post it.


4.45:1 - M40 316i and 318i automatic, plastic bumper models. Plus plastic bumper 320i Auto.
4.27:1 - M40 316 Manual. Plus some plastic bumper 320i Tourings.
4.1:1(small)- M40 318i/318is. Post Aug. 85 320i (195/65), 320i (15" BBS)
4.1:1(small)- 318is and 320i with LSD
4.1:1(big)- USA market M3. Post 1985 320i option with LSD
3.9:1(small)- Post Aug '85 316/316i and 320i, M10 316/318i auto, 318 5 speed
3.9:1(big)- 325i Sport auto/manual. 25% LSD. Also 325iX manual.
3.74:1(big)- 325iX automatic, 25% LSD (Not GB).
3.73:1(big)- Plastic bumper 325i.
3.64:1(small)- M10 316, 318 four speed manual.
3.64:1(big)- 325i chrome bumper inc. many 1986/7 Sport (with LSD for Sport).
3.63:1(big)- 325i (plastic bumper) and 320iS (optional)
3.46:1(big)- 323i (9/84 onwards), 325i Automatic, 320iS (LSD)
3.45:1(big)- 324td (Not GB)
3.45:1(small)- 320i and early 323i manual with 195/60 tires.
3.23:1(big)- 323i with sports gearbox, most with 25% LSD, 324td, non-LSD
3.25:1(big)- M3, 2.3 cars except Evo II
3.15:1(big)- M3 Evo II and 2.5 litre M3 Evo Sport 3. Also Z3 2.8/3.0/M
2.93:1(big)- 325e (Not GB)

Big differentials are basically a bigger casing. They have 8 bolts instead of the small casing 6 bolt covers.
The higher the number(lower gearing), the better the acceleration. Lower number(higher gearing), better top speed and lower cruising RPM.
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To me, a car with an automatic transmission seemed like a toy for grown-ups. All you have to do is steer? Where's the fun in that?
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ten2doyle102
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Re: Final drives - what comes from what?

Postby ten2doyle102 » Mon Mar 23, 2009 3:25 am

Good info! I call sticky!
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Re: Final drives - what comes from what?

Postby M20_fever » Mon Mar 23, 2009 5:38 am

so are the 325i diffs the same for the 'is' models?
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Re: Final drives - what comes from what?

Postby joecrotch » Mon Mar 23, 2009 11:00 am

so are the big diffs interchangeable with the small ones?
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Re: Final drives - what comes from what?

Postby Yoshi » Mon Mar 23, 2009 1:34 pm

from what i know, yes. I had a small case 4.10lsd on my turbo car and didn't know it. Didn't break it either.
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blacke30
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Re: Final drives - what comes from what?

Postby blacke30 » Mon Mar 23, 2009 3:24 pm

M20_fever wrote:so are the 325i diffs the same for the 'is' models?



I think 325i Sport is the same thing as 325is.
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To me, a car with an automatic transmission seemed like a toy for grown-ups. All you have to do is steer? Where's the fun in that?
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Re: Final drives - what comes from what?

Postby ejohnson » Mon Mar 23, 2009 6:34 pm

I would just like to point out that e30s did not come with "big" case diffs, we had the "medium" case. e28 m5s and 7s came with the "big" case diffs.
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Re: Final drives - what comes from what?

Postby BMWIS » Mon Mar 23, 2009 7:42 pm

Yeah and those numbers don't really jibe with what I've seen elsewhere.

Possible that is euro diff availability.
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Re: Final drives - what comes from what?

Postby ejohnson » Mon Mar 23, 2009 8:09 pm

3.74:1(big)- 325iX automatic, 25% LSD (Not GB). Is also wrong, 325ix autos came with 4.10 gears.
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Re: Final drives - what comes from what?

Postby blacke30 » Sat May 02, 2009 2:47 am

BMWIS wrote:Yeah and those numbers don't really jibe with what I've seen elsewhere.

Possible that is euro diff availability.


Might be since the book was written by a British guy.
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To me, a car with an automatic transmission seemed like a toy for grown-ups. All you have to do is steer? Where's the fun in that?

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