joeb Posted January 14, 2006 Report Share Posted January 14, 2006 My 96 STS has a 3.73 final drive ratio. I also have a 97 grand prix GTP but that has a 2.91 ratio. I believe the GT's or maybe the SE models have a 3.23 ratio or thereabouts which helps the acceleration since they has less torque. lets say both of my cars make the same torque but the GP weighs about 400lbs less. does that mean the GP can live with the lower numerical ratio since it has less mass to accelerate? ya, I am not accounting for the trans gear ratio's (1-2-3) but I asssume they are similar. Link to comment Share on other sites More sharing options...
JasonA Posted January 14, 2006 Report Share Posted January 14, 2006 Your STS has a 3.71:1 final drive. Typically, an automaker can put a numerically lower final drive in a vehicle with a better torque curve and achieve similar results -- but return maximum mileage. Like the STS vs. SLS. The STS is 3.71 and the SLS is 3.11. Actual field performance is similar because of the SLS's torque advantage (although the STS should ultimately win). The mileage factor is much better on the SLS. Our Grand Caravan has the small V6 (3.3L). It has a numerically higher final drive than the Grand Caravan with the big V6 (3.8L). Again, the big V6 has more torque (245 vs. 210) and can easily work with the numerically lower gear and still provide good mileage. I suspect the same deal goes with your Grand Prix. In addition, the naturally-aspirated Grand Prix engines need more engine speed to make power than your supercharged 3800 does...thus, their numerically higher final drive. Your supercharged 3800 makes good power down low, so they can use a numerically lower final drive to strike a good balance between performance and economy. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
joeb Posted January 14, 2006 Author Report Share Posted January 14, 2006 I had a 79 camaro that had a 2.41 rear. bonneville gears I think. thats how you coax a bit more mileage out of a car. I swapped in another rear with 3.73 gears that really helped the acceleration. I had a 350 trans and the highest speedo gear for an auto than was 3.41? so my speedo was always off a bit. i never really watched my speedo since i just kept up with traffic. the 350 trans did not have OD so it really wound out the motor. kinda annoying with a loud exhaust. my GTP has a CAI, smaller pulley, aftermarket PCM, and custom exhaust so it moves pretty well. I can never remember if my STS has 3.71 or 3.73. Link to comment Share on other sites More sharing options...
JasonA Posted January 15, 2006 Report Share Posted January 15, 2006 My '84 Cutlass had a 2.14:1 rear gear (yes, that's not a typo). That rear gear was exclusive to the V8 cars with TH-200-C transmission (3 forward speeds). If you got the V6 engine, it came with a 2.56:1 rear gear, since the little 231 V6 just didn't have enough oomph to get it done with the 2.14s. If you got a Cutlass in Canada and ordered the V8, it came with a Chevy 305 and a 2.41:1 rear gear...the Chevy 305 didn't have as good of a torque curve as the Oldsmobile 307...and thus didn't come with quite as tall a gear. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
thu Posted January 15, 2006 Report Share Posted January 15, 2006 Wouldn't you think it would be wonderful if they offered two-speed final ratios? Yah. 2003 Seville STS 43k miles with the Bose Sound, Navigation System, HID Headlamps, and MagneRide 1993 DeVille. Looks great inside and out! 298k miles! Link to comment Share on other sites More sharing options...
stsjoe Posted January 15, 2006 Report Share Posted January 15, 2006 Iwas running a 455 in a 73 Formula with 3:73's talk about RPM happy problem was it would brake traction TO easy, I had to get rid of it before it got rid of me! Link to comment Share on other sites More sharing options...
tjtjwdad Posted January 16, 2006 Report Share Posted January 16, 2006 stsjoe Posted Today, 06:31 AM Iwas running a 455 in a 73 Formula with 3:73's talk about RPM happy problem was it would brake traction TO easy, I had to get rid of it before it got rid of me! That's what I have in my 70 Trans Am and you're right, on a wet pavement it can become a handfull ... in a hurry! Jim Link to comment Share on other sites More sharing options...
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