Danno74Z Posted April 3, 2011 Share Posted April 3, 2011 I would like opinions on which final drive ratio(3.9 or 3.7) I should use behind a LS1/T56 engine transmission combo? Also is 1 gear useless except at the drag strip to heat up the tires Just use second gear from a stop? Thanks. Danno74Z Quote Link to comment Share on other sites More sharing options...
johnc Posted April 4, 2011 Share Posted April 4, 2011 I would like opinions on which final drive ratio(3.9 or 3.7) I should use behind a LS1/T56 engine transmission combo? Also is 1 gear useless except at the drag strip to heat up the tires Just use second gear from a stop? Thanks. Danno74Z Its a 5% difference. That's probably 300 rpm. Quote Link to comment Share on other sites More sharing options...
Danno74Z Posted April 6, 2011 Author Share Posted April 6, 2011 Thanks John. Danno74Z Quote Link to comment Share on other sites More sharing options...
rejracer Posted April 22, 2011 Share Posted April 22, 2011 I would go with the lower gears with a t56. The gearing on the T56 was originally with with lower diff ratio's. What did the doner car have in it? What do you intend to do with the car? In choosing gears, it's best to set your highway cruise speeds with the differential ratio, (assuming a fixed high gear ratio), and choose the transmissions 1-3 ratio's from there. Since you are past the planning point as far as transmission gearing, what are the transmissions ratio's? if 6th is .68 go for the 3.70s, if it's .5 then go for 3.90's (or lower). I build a speed / RPM calculator for just this purpose. You might want to check it out: Speed - RPM Calculator Quote Link to comment Share on other sites More sharing options...
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