Changing Final Drive Ratio

[Muzzman]

I'm finally having an LSD fitted to my track car that has been sitting in the garage for ages.

Car is a BMW 325ti with a m52b30 fitted.

The car currently has a 3.23:1 final drive ratio.

While the diff is out is it worth getting this fitted?

https://www.ebay.co.uk/itm/166298728762?mkcid=16&a...

There is a 4.10 option but that might be a bit much.

Tracks are mainly Snetterton, Brands and Goodwood. Annual trip to the ring might be a bit tiring though.

[The Conflated Outlier]

A 3.46 from a 325i or 328i Auto - if you can find one.

[911Spanker]

I have a 3.73 ratio diff from Birds on my 328 road car. It's ace!

[Muzzman]

Apparently that one I linked to doesn't fit.

I'll try and hunt down something suitable

[Muzzman]

The Conflated Outlier said:

A 3.46 from a 325i or 328i Auto - if you can find one.

Wouldn't that be a bit of a pointless change from a 3.23?

[Muzzman]

Would this fit a 325ti compact 5speed?

https://www.ebay.co.uk/itm/225955154338?mkcid=16&a...

[The Conflated Outlier]

It will.

It's not an E46 330i diff either - too small for that. Those things are the big type 210 with the six bolt CV type rear prop joint and big driveshaft CV's.

It's from an N52 Z4 3.0Si Auto. It's the same type 188 as yours (medium case) but with the Z4 finned rear cover for oil cooling - it also has the correct four bolt prop flange. Two hours of swearing and it'll be in.

With that ratio it will be very lively in top gear. It shouldn't be horrendous on long trips either.