(I also posted this on N54tech)

We just picked up an 05 530i M54 w/6-speed manual tranny for my son.
This puts us up to three bimmers to play with!!

This M54 is the same motor I have in my e46 vert but seems much slower in the 530i. I do have the ZHP, which changes hp (+10) & slightly deeper gearing, but the 5-series actually WEIGHS 225 lbs LESS than that 3-series (3,475 vs ~3,700). We'd like to make the 530i more fun to drive without spending a lot of money.

So anyway...
The 6-speed seems like total overkill on that car, so I was wondering if a quicker final drive could be swapped into that rearend (I know usually autos have shorter gears). Or would the whole rear need to be swapped. I obviously don't know too much about this, except theory.

The car would be quicker, and I really don't think he'd lose much in fuel economy.

Thoughts?

And how hard is something like this to do??
Shade tree, enthusiast, or true mechanic??

Thanks guys, I appreciate any feedback.

// Radar //

2010 535i M-Sport w/Sport AT, Alpine White w/Natural Leather --- JB4 G5 ISO w/BMS RACE Flash, Custom Meth w/dual CM5s, VRSF 3" Down Pipes, MMPe DCIs, Wagner 1060 Stepped FMIC, VRSF Chargepipe/Tial BOV