5-speed or 6-speed for your supercharger

[MachRc]

So how many of you guys have a 5 speed supercharged e46?? Any downside or upside to having a 5-speed compared to a 6-speed??? will having a 5-speed and 2.91 differential effect hp and tq. numbers on a 330ci? just real curious wether I should look into shorter final drive b4 I go FI -TIA

[TxZHP04]

The first 5 gears are basically identical between the 5 and 6 speeds. 6th gear provides overdrive, if you haven't needed it before you won't need it with a SC. Changing to a shorter diff would increase rpms at all road speeds, making 6th advantageous for highway cruising.

There are lots of factors that go into selecting a diff ratio. What kind of SC are you considering? Shorter gears are generally described as providing a torque multiplication effect. This may or may not be what you are looking for. It's not uncommon for FI folks to go with taller gears, going with something like to 2.91 instead of something much shorter.

Honestly, I would recommend getting your supercharger and then see if you think you need shorter gears. Personally, I'd be thinking LSD before shorter gears (although if you wanted to do both it would be best to do them at the same time).

[2003330i]

check this out http://forum.e46fanatics.com/showthread.php?t=356779

[MarvelPhx]

I have had both a 5-speed and 6-speed with SC. The rear gear matters more than the difference between the transmissions.

[MachRc]

thanks guys for your reply. I was driving today and noticed in traffic that the longer ratio 2.91 and 5 speed helps alot since Im in gear all the time and love "engine braking" at a low2.5k -3.5k rpm. Most times Im up in the mountains/track I noticed Im in 3rd the whole time. Do you FI guys keep your car in gear as much as I do?? I know the BPV does its thing when you let off the gas lets say 4k rpm, but will keeping it in gear and letting the rpm drop and slowing your car effect longevity of the engine/SC??