Diff Ratios.....What's best???

[NZM50SWAP]

I think My gearing is to tall......

I've just switched my diff from a 4.1 open to a 2.93 Lsd
My setup is e30 nonvanos m50 2.5 m20 ZF 5spd with m20 clutch and flywheel.
I'm finding it really hard to drive around town. Open roads it's good but still I accelleration isn't quite there after 3rd gear. 1st redline = 65kmh 2nd redline =135kmh 3rd redline = 170kmh 4 redline = just shy of 240kmh and 5th barely accellerates.

What's the best ratio to used with the m20 gearbox. I'm thinking probably about 3.46 would be good ....

Any Ideas???

[browntown]

3.25 might be easier available off an old 5'er, or try the plentiful 3.73

edit: use unixnerd to crunch the numbers, google him

[DanThe]

Prob be cheaper to get a gearbox from an E36 325i, that diff would be perfect then

[Mike B.]

Here is a good gearing calculator - http://www.diffsonline.com/techinfo/...Calculator.xls

I had a 3.46 on my M50 swap (E36 Getrag trans). Accel was great, but I was turning big revs while cruising on the highway, around 4k @ 80 mph.

I am probably going to use a 3.25 with my Euro swap (M3 ZF trans).

For the stock E30 getrag trans, I would go with the 3.73 or even a 4.10.

[NZM50SWAP]

Prob be cheaper to get a gearbox from an E36 325i, that diff would be perfect then

Whats sort of things would I need to change to a e36 325i gearbox.
Wouldn't I need to change my driveshaft, clutch and flywheel, starter???

Diff's are cheap down here so would probably be cheaper to change that.

[joshh]

Why change the tranny when you can simply change the diff??
There isn't a "best". Find the one that would be best for you. If you feel your gearing is too short, get a taller one and try it.

[Mike B.]

The nice thing about the E36 trans (Getrag) is that is uses the stock 5-spd E30 325i/is driveshaft and transmission bracket (no custom job necessary).

I'm not sure if you could use your current flywheel/clutch package or not. Hopefully someone will chime in.

[DanThe]

Yes you can use the M20 fly/clutch/starter, same as my setup with an M3 3.25 diff which feels a bit too high for my liking

*edit* high as in lots of acceleration and low top end

[iwantone]

i recently bought a 323i with an m50.
it is using the stock 323 tranny, but with a 3.73 diff.
the car runs at about 2600rpm at 60mph, so not too bad.
but i accelerates great, even through 5th gear.

[Mot]

Im running a ZFm3 trans and 3.25lsd combo, I really like it so far.

[tjhartge]

If you have the m20 OD gearbox,
I'd say go for 3.46 if you are in alot of freeways, and 3.64 if you are in town alot.
If you track the car often, either a 3.73 or 3.91 would be about right.

Another factor would be the current flywheel/clutch setup you have now, is this the singlemass or twinmass or doublemass m20 flywheel?

If i was running any of the combinations below, this is what i would be running

singlemass = 3.46
doublemass = 3.73 - thick and heavy version of the singlemass
twinmass = 3.64 - similair to the newer twinmass, with springloaded inbetween the masses

[NZM50SWAP]

Using single mass m20 flywheel that's being lightened somewhat.
Yeah I think I'm going look for a 3.64LSD

[Brew]

If you are using the E30 getrag, stick with a 3.73 or 4.10. The gearing doesn't change because of the engine you're using.

[nando]

If you are using the E30 getrag, stick with a 3.73 or 4.10. The gearing doesn't change because of the engine you're using.

no, but with more torque coming from the engine, you don't need the extra mechanical advantage from say a 4.10 LSD anymore.

[FredK]

3.73 is probably best, especially with an M50.

With a .81 5th gear, your final drive ratio is 3.02, which is actually lower than a US E36 M3, which had a final drive ratio of 3.15 or 3.23. You'll turn around 3700 rpm at 80 mph (129 km/h).