Looking to get a longer diff on my e30 m3

[m3j0n]

just took the e30 m3 out for a drive and, while the acceleration is nasty, I hit top speed very fast and highway driving is almost unbearable over long distances.

[m3j0n]

very difficult to quantify this; a gearing change will be much easier to compare.

Fuel data for Average combined Fwy/local driving (prior DD's)

1998 M3 3,23->3,46 = decrease 24-25 MPG to 22-23 MPG
2003 325i 3,15->3,46 = decrease 25-26 MPG to 23-24 MPG
1992 525i 3,23 ->3,15 = increase 23-24 MPG to 24-25 MPG

the more modern m54 engine with is double vanos and can bus electronics is much more conservative on fuel on freeway cruising; its 29-30 mpg.
Obviously 3200cc vs 2500cc is another issue regarding mpg.

Choose the final drive that suits your desired MPG for the kind of driving you enjoy. Stock BMW is always good

can you pm me a quote on the labor to build me a 3.25 LSD?

[lukeADE335i]

Thanks Wangan. My Dad is about to try a 3.25 small case in his 320i. I'm thinking it's too low, but he's mostly cruising on the highway on a flat road, so it should work ok. Going from a 4.10 to a 3.25 will make a big difference to cruising RPM.


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[Wanganstyle]

Any idea how much difference to economy would this make? Always interested in making the car better on fuel. :)



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very difficult to quantify this; a gearing change will be much easier to compare.

Fuel data for Average combined Fwy/local driving (prior DD's)

1998 M3 3,23->3,46 = decrease 24-25 MPG to 22-23 MPG
2003 325i 3,15->3,46 = decrease 25-26 MPG to 23-24 MPG
1992 525i 3,23 ->3,15 = increase 23-24 MPG to 24-25 MPG

the more modern m54 engine with is double vanos and can bus electronics is much more conservative on fuel on freeway cruising; its 29-30 mpg.
Obviously 3200cc vs 2500cc is another issue regarding mpg.

Choose the final drive that suits your desired MPG for the kind of driving you enjoy. Stock BMW is always good

[lukeADE335i]

I always fit the late model E36 gears as they are a updated more efficient design than the earlier e28/34 gears. Some won't care about this; BMW revised gears for efficiency mid 90's and then again late 90's in the e38/39/46

Any idea how much difference to economy would this make? Always interested in making the car better on fuel. :)



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[agent]

For the ZF gearbox, 3.15 is the perfect ratio for street/highway driving with some AutoX and/or track days sprinkled in.

[Wanganstyle]

Probably more pricey than sourcing a used diff though, right?




AWESOME info! Thanks for being the guinea pig!! LOL.



cool. thanks.

Much more but new everything is just that

If you have a rear end shop local to you that knows BMW units they can just re-configure your original differential from 4,10->3,15. Lots of labor to expense.

I always fit the late model E36 gears as they are a updated more efficient design than the earlier e28/34 gears. Some won't care about this; BMW revised gears for efficiency mid 90's and then again late 90's in the e38/39/46

[m3j0n]

Wanganstyle (on here) builds 3.15 torsens for the E30. I just picked one up. PM him. He knows rear ends and can build pretty much anything.

Probably more pricey than sourcing a used diff though, right?

I have an S3.25 with my S50/zf, best all around ratio i've tried. S3.46 was great fun but too many rpm's. S2.93 is great for cruising but sucked a bit of the fun out. It is a toy after all.

i'm building a 3.15 now, got the gears from an e36

AWESOME info! Thanks for being the guinea pig!! LOL.

The 3.25 LSD is common in the e28 535i - that's where I got mine from.


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cool. thanks.

[lukeADE335i]

The 3.25 LSD is common in the e28 535i - that's where I got mine from.


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[e30rapidic]

I have an S3.25 with my S50/zf, best all around ratio i've tried. S3.46 was great fun but too many rpm's. S2.93 is great for cruising but sucked a bit of the fun out. It is a toy after all.

i'm building a 3.15 now, got the gears from an e36

[ajhostetter]

Looking to get a longer diff on my e30 m3

Wanganstyle (on here) builds 3.15 torsens for the E30. I just picked one up. PM him. He knows rear ends and can build pretty much anything.

[m3j0n]

yeah.. trying to find one now... they are either priced high, or sold....:(

[MR 325]

A 3.25 ratio is just about perfect for that engine and trans combo.

[m3j0n]

ok, cool.. thanks... I don't think Ill be finding a 3.15.. that must be ultra rare.

[FredK]

Yes. The Z3M has the same case-style as the E30 (and E28/E24/E23). It is incompatible with the E36 diff.

The S54 Z3M had a 3.15. The S52 Z3M had a 3.23.