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Rear Axle Ratio

Started by may2022, May 05, 2022, 12:54:06 PM

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What would you pick, 3.23 or 3.42 rear axle ratio?  345hp/420tq 403 olds TH350 stock converter, currently has 2.41 axle.  Occasional highway round trips of 60 miles, other than that usually cruising in town.  We live out of town so always have a 4-mile highway drive to get into town.  I was leaning towards the 3.42's but now having some second thoughts on it being too steep.  No interstate driving really at all.
Scott Turchin


Without an overdrive, I'd personally prefer a 3.23 or 2.93 and a slightly loose torque converter (something that stalls near but under 3000 rpm). The thing with an automatic is you can compensate for a taller final drive by running a higher stall and still get the same torque multiplication as a shorter final drive but retain sane highway RPMs. Especially if you're running a lockup torque converter. A 3.42 or 3.73 would be best if you were running a 200-4R or a manual transmission.

Frank Gore
National Firebird and Trans Am Club
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