4:10 or 3:73 for mostly drag use?

[wenbeaver89]

First a few stats on the car! 87 325is m50tu turbo, right around 300whp. Mostly just a dd but take it to the drag strip with my buddies! I only went once so far and got 4 runs in, my best time being 14.2 @ 100mph. I know i should be able to do alot better than this but the trak was getting a bit slick. I think my best 60ft was like 2.3 and most of them were 2.5ish. I am running the getrag 260 with a 4:10 diff and it seems like 1st gear is pretty much useless. Would a 3:73 do the trick or should i go longer yet? Thanks

[dustyperez]

I'd think 3.25 would be better,

[MF DOOM]

Most 24v guys seem to be running 2.93

[wenbeaver89]

what does the 3.25 come out of?

[dustyperez]

e28 has 325's

[kamotors]

3.15 torsen:)

[Wh33lhop]

Most 24v guys seem to be running 2.93

That is because they are using the E36 transmission, which he is not.

OP, I would either start in second (if you can spool at low rpm) or try something much longer, like a 3.46 or 3.25.

[agent]

3.15 torsen

...with a ZF.

[wenbeaver89]

Thanks guys! looks like ill be trying to find a 3.25!

[Poorboyz]

As mentioned above the E28s have them. I pulled a 3.46 and 2 3.25s from E28s at the local yard.

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[mulletman]

What sort of speed will your car run? With a G260, 3.25 is way too tall. Here are the speeds you'd be getting in each gear, assuming a stock-ish tire size and a 7000 RPM shift.

1st: 40
2nd: 69
3rd: 108
4th: 152
5th: 187

A 3.73 would get you the following:

1st: 35
2nd: 60
3rd: 94
4th: 132
5th: 163

With your current 4.10:

1st: 31
2nd: 55
3rd: 86
4th: 120
5th: 149

I really doubt your car will be breaking 120... So I would stay with the current gearing and launch in second. That way you only shift twice and long gearing doesn't cause bogging. If you got a 3.25 you'd only use the first three gears, so still only two shifts, but the gears would be so wide it would be dumb. Think motorcycle gearing... Super tall first gear, but then tight ratios after that.

There are other options if you want to go find a ZF gearbox.

[Kershaw]

^ great post. beat me to it. you really want to keep the shifts to a minimum. shifting to 4th right before the finish line is a killer, costs you ~.2 seconds right there.

you really need to get your 60' down to sub 2 second times.

[wenbeaver89]

Ok thanks guys that speed list is great! :) Unfortunetly my ebay(yes never get one) manifold cracked so i'll be getting a good & tight one and the diff will have to wait. Might not be a bad thing and i think with some practice i can launch in second and get my 60ft down. It did really tick me off that i had to shift into 4th right before the line but i had to or i would hit r3vlimiter! :)

[DREWHALL]

I am using a 3.73 on my S50, I ran 13.4@106 with a 2.1 60' on 205/50/15 ET Streets. I couldn't get a decent burnout because it started wheel hopping really bad, so I left them cold and I was spinning big time through first and second gear. That being said the 3.73 is good on the street, and plenty for me on the track.

[wenbeaver89]

That sounds more like it and thats a pretty good time!! I've been trying some practice launches in second and i'm not sure if i like it. Really gotta burn the clutch! :( You have anything done to your s50?