I posted this elsewhere, but think it applies here as well....
I am new here, but not new to this topic. The final ratio for the rear is not the end all answer for a proper setup. And if you are like me and looking for a car that you use as a spirited daily driver and will occasionally track it or want to not be embarrassed on the light to light romps with a scrappy young kid in a nice ride or head to head with another fast ride on the open roads. Yet you aren't about to dump a ton of money into a crate engine prepped with a supercharger or the mods required for a turbo setup , then you're going to go the route of bolt ons and power tune tweaks like the majority of the rides out there and leave that 5.0 Coyote normally aspirated.
Horsepower and the final drive ratio derived from a combination of the Rear Axle ratio, Transmission gear ratios and the diameter of your tires will determine if your setup is better than the other guy's.
If you go with a 3:55 rear axle mated to a 3:66 1st gear on the Manual Tran ...since the GT manual tranny ratios are what "they are", unless you modded your tranny. Then launching around 4000RPM you can go with a track setup of 17/18 inch slicks and whip those wheels at the same rate as a GT with 20 inch street tires and 4:10 rear axle. Considering most young guns go for looks over setup... you'll likely come out on top every time on track day. Just keeping in mind your car is setup for more than just track. With this setup you can stomp most 3:73 setups on 19's all day long. Depends on what they swap their tire to ... if they in fact do so. A lot of guys just run on street tires.
Then with some bolt on power additions when you're back on the street you can run with 20 inch diameter tires and find your self in still in a close run with a Stock GT Brembo running on 19 inch diameter tires. BUT, the difference is from a roll.. since you're gonna always be a bit faster with your setup. You can Whine the tranny in 5th gear and have more top end and just roll on by the other other guy. Its fun too, because you can actually creep on em coming up the side and reeling them in. From a 60mph Hgwy roll from 4th gear to 5th you're always going to beat down a 3:73 setup on 19 inch tires even similar to yours in HP. Tap that sweet spot on the power band from 5500 to 6500 RPM and you'll flyby easy. Don't hit 6th unless you want to bog down and see taillights.
From light to light its a drivers game...depends on hitting the shifts "spot on" and of course the final HP/torque you have pushing that gearing in the sweet spot RPM range. So a nice fat Exhaust with a FAT "H" pipe or Crossover, premium gas timing tune and a bigger wider cold air intake on wide fat sticky street summer tires usually does the trick for HP and torque gains through the lower RPM range.
For more oomph behind this on top end you can do other bolt ons like wider throttle body or a Boss 302 intake...but then you can expect your low RPM to take a bit of a hit. Again its about finding your sweet spot.
The bonus with the 3:55 setup is a good pocket for performance and economy. Its easier to swap tires and apply a tune than it is to swap ring and pinion. So for a dual purpose car... there's a reason a GT/CS or a PENSKE Special Edition is setup with them.
I have three sets of wheels and tires. Track, Summer and Winter.
17" track, 20 inch summer, and 19 inch Winter wheels.
Adjusting to the slightly smaller diameter in the winter helps with traction starting from 2nd gear during inclement weather. I'm considering 18 inch tires. But the 19's served me well.
Last edited by Cruzinaround; 08-17-2013 at 06:22 AM.
Reason: Omit quote