Changing final drive ratios

[sumotan]

Hi Gents,
I came upon an old thread discussing the above on E85/86. Was wondering has anyone done this for E89 especially for the N20.
Final drive specs for example my 28i is stated 3.077 would be great if we can get a higher ratio for better acceleration between gear changes.
At my end I'll never be able to ever see top speed so improving acceleration is a good compromise. Ideally the right way is to change the gear box ratios instead but cost is gonna be prohibitive so no logic here

As always thanks

 

[mcbutler]

I dont know about other spec Zeds but the 35i/is have the crown wheel welded in place, you cannot just unbolt it and swap it over. Seems a lot of work to create a car that would be marginally faster with questionable driveability to say the least

 

[brillomaster]

well on an old e46 and e85 its pretty straightforward, get a diff with a more favourable final drive ratio and swap them over.

i remember i swapped the diff on an old 328i from a 2.97 to a 3.38, made a noticable difference to how it accelerated through the gears, and was only 300rpm higher or so when cruising on a motorway.

if you genuinely find yourself thinking 'this gear feels long' then i'd give it a go. might be more tricky if theres any fancy electronic torque biasing gubbins going on in the diff, but if its purely a mechanical, open diff then i dont really see any problems with swapping them over.

 

[sumotan]

Thanks Gents well if it can be done easily then it might be a gd option to experiment. Posted this as I couldn't find any info on the web with regards to E89 differential tweaks.