Rear end questions about my Mustang.

[Doug_Guilds]

I have a 2.14 second gear 4 speed with a 3.08 gear. Tires are about 68-71 inch and i can only get about 5800 rpm on a tight 1/4 mile track. I want 7200 max, 6800 min. I am planning on going to a 15 inch wheel to give me a lot more tire size choices next season.

Can I go with a 3.40ish gear and maybe around a 75 inch tire and not be over geared or go with something like a 3.25ish gear and maybe run a 72 inch tire? (I am not sure the exact numbers for the 6.75 rear end gears so that's why I say .25ish)

I run the 6.75 because of the weight savings on my unsprung weight but would it benefit me more to run the 7.5 and have the better choices of gear ratios and sacrifice the weight savings?

[car62]

you are going to be limited on the gears for the 6 3/4 rearend,they dont make a 3.25...i think 3.18 is as high as it goes in a Pinto style and 3.08 for mustang style.

[mkfnbc]

I run on a 1/4 mile track and run the 7.5 rear end. I run a 2.14 and 3.73 gear and pull 7800. I can drop that to 7200 by running a 3.45 gear. Anything less than that at our track can't keep up.

[car62]

each track is different..i run 2.14 with a 3.08 and turn 7400-7500..put in 3.27 and turn right at 8000-8100

[pinto21]

if u running a tight conner 1/4 mile track need a 373 if it not so tight run a 345

[Headhunter]

Gear choice really depends on motor. If this is a pure stock division then he needs to keep the RPM to match power output and RPM's desired. Now if it is a lightweight good race motor that will acceleate faster and turn more RPM the gear needs to be adjusted for that. We can give you a idea of what you need to match your car, motor and track but the choice is up to you.

[Old Rob]

There is a trans, rear gear = final drive chart in the technical section at www.powerbyace.com