rear end/rpm

[rexzilla_03]

(m44 5 speed) so the thing is, i sometimes travel with my car, on the highways i do 80, and at that speed im doing 3750rpm, i would like to bring that rpm down a bit, im going to be putting an lsd in eventually, and i want lower rear end gears then what i have which i believe is the 3.45 gears, first gear is pretty much worthless, and second gear isnt too great either. lower rear end gears will make them better, without sacrificing too much of acceleration (im hoping) and be able to cruise at lower rpms on the highway... i know its perfectly normal for it to be right at that, if i want to go any faster say 90 im at 4200 rpm, and i just dont feel comfortable screaming down the highway for hours... what should i look for? 3.23 gears? what kind of difference would i be looking at?

[rexzilla_03]

nobody?

[BeRzErKaS]

http://www.meeks.f9.co.uk/sunbeam-racing/gearing/Gearing.xls

^Download this excel spreadsheet program and set it up as shown below. I put in what I believe are the correct spec for your 318 (OEM tire size, Getrag trans ratios, etc). Double check them. With the specs entered I come up with 3760rpms @ 80mph which is pretty close to what you mention.

http://i37.tinypic.com/sevddh.jpg


Play around with the box in the bottom left that says diff ratio to see how your RPMs will be impacted at your designated cruising speed.

[bitterbimmer]

what is the differance in the 3.73 and the 3.23 rear ends which one lower your rpms. I have a 94 325i with the 3.73 rear end 1 gear will get to 25mph, 2 gear about 50, 3 will push it up to 93, 4gear 118, 5 gear up 130 then am tap out by that nasty govner so if you can help me find out the differance in the three

[BeRzErKaS]

what is the differance in the 3.73 and the 3.23 rear ends which one lower your rpms.

Lower gear ratio = "longer gears" = lower rpms

Higher gear ratio = "shorter gears" = higher rpms


I have a 94 325i with the 3.73 rear end 1 gear will get to 25mph, 2 gear about 50, 3 will push it up to 93, 4gear 118, 5 gear up 130 then am tap out by that nasty govner so if you can help me find out the differance in the three

Hmm... I ran a 3.91 for about 2 years and just recently switched over to a 2.93. Your speed/gear number sound like what I have now with the 2.93.

With the 3.91 I was in 5th by like 45mph. Highway cruising at 70mph/4500rpms.

I must say, it's pretty nice to have a 1st gear again. I used to just start off in 2nd. Plus the car so much quieter now.

Haven't been to the track yet to see how my 0-60 has been affected but making only 3 shifts to 60 has to be faster than making 5.