The Mustang Forum for Track & Racing Enthusiasts

Taking your Mustang to an open track/HPDE event for the first time? Do you race competitively? This forum is for you! Log in to remove most ads.

  • Welcome to the Ford Mustang forum built for owners of the Mustang GT350, BOSS 302, GT500, and all other S550, S197, SN95, Fox Body and older Mustangs set up for open track days, road racing, and/or autocross. Join our forum, interact with others, share your build, and help us strengthen this community!

Rear Gear Ratio

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Has anyone swapped out the stock 3:73's? I've read about Fox Bodies with stock Coyote motors and steep gears (4:88 etc) running high 10's in the 1/4 mile. The Boss 6 speed makes the rear gear close to a 4:10 if compared to a Tremec. It just seems like a cheap mod that would not void warranty. I'd really like to try 4:30's with drag radials. Is there a speedo gear to swap out to correct the speed or must it be done by the computer?


Lord knows I'm a Voodoo Child
Exp. Type
W2W Racing
Exp. Level
10-20 Years
Cookeville TN
Make sure you take into account tire size. Stock wheels/tires are 27.1" tall, If you go to 17 or 18" Drag tires you can reduce height and effectively lower gearing. Tire rack has revolutions per mile in the specs of the tires they sell and you can find calculators on google to run the numbers.


Because racecar.
Arizona, USA
Also if you're talking about drag racing, you'll want to take into account your max speed in 4th and 5th when considering your gearing--but you will be doing a LOT of shifting with a shorter rear gear.
The only 19" drag radials I've seen are taller that the stock tires. I lean toward keeping the stock 19" wheels because I like the stock look. The M/T tires are 28" tall. They might be better paired with 4:30's. Maybe I'll end up being the test mule. I just hoped some one on here had swapped gears. Has anyone used the the 28" tires with the 3:73's? If yes, what was your RPM through the traps. I assume you be in 4th gear.

TMO Supporting Vendors