Transmission/Axle ratio question.

[bigvegan]

Okay, here's a question I've got that maybe one of you guys can answer.

If you're building a pro-tourer for drag/ autocross / track days / open road racing, and you'd like to have a single vehicle for all three, what are the best ways to calculate the rearend/transmission ratios that will be best able to handle the HP and help you achieve those three somewhat different goals? I'm still in the mental building stage, and I'm trying to get an idea of how to build something that's halfway decent for drag/stoplight contests, but will still have plenty of top end speed.

Obviously there are going to be some compromises involved, but what's the best way to calculate out the different ratios for the transmission and rearend gearing so that you can have a car that's as well rounded as possible? (e.g. are there any quick and dirty equations that let you know what your approximate 1/4mile time and top speeds will be for a variety of ratios?)

Thanks in advance!

[bigvegan]

http://www.chevyhiperformance.com/te...o_calculating/

The article is at the link above if anybody else had a similar question.

[Kenova]

I would think that a T56 would also help you reach your goals. With low gears in the rear you would easily meet your goals on the drag strip and the overdrive gears would still give you ratios you could use on a road course. I'm not sure if drive shaft rpm would be a big concern, but a quality driveshaft would probably be a good idea.
If you were to use a 9" rear it would be easier to try different gear ratios to nail the one that suits you best.
Ken

[Goatman]

Gear Vendors..

[mikes69z]

My feeling is go with a total of about 10:1 or 9:1 for first gear and make high gear whatever you want to cruise at. A six speed is probably the better option since it will give you closer ratios and flexibility for the different things you're planning on doing with the car. Perhaps a T56 or a ROD. And watch your driveshaft RPM - ciritcal speed is nothing to be taken lightly.