I have a 302 small block, 4 barrel Holley, RPM air gap intake, b303 ford racing cam with 480 lift, aluminum pro comp 210cc heads, Roller rockers, holley 90psi electric fuel pump, t5 5speed trans. I was giving a 9inch ford rear end from a buddy in oklahoma and i need to rebuild it. Im not going to drive my mustang on the highway much, if at all, so i want a pretty high gear from great launches and accel. What gear should i get? Also if someone had a guess, How much HP could my motor make?

Thanks
Aaron

 

I restored a bunch of Mustangs, but I don't build street racers and am just a novice mechanic at best so I'm certainly no expert. As far as a daily driver application goes, if you aren't going to be on a highway much, 3.66 gears will give you plenty of punch. I have 3.50 gears in a stock 8.5 rear with a mostly stock drivetrain, and it's pretty responsive compared to the 2.79 stock rear. JMO.

CP

 

hell with the t5 you could run 4.11s and turn 3000 rpm at 80mph....so 4:11s are totally doable. The problem is I dont know how much torque that motor will produce but im guessing its going to be over 340. it sounds pretty tricked.

so even though 4:11s are not an issue rpm wise you might hate life trying to get them to do anything other than turn tires into smoke.

If you are indeed close to 350 FtLbs a 3:55 would be a better choice

-Gun

 

If i remember right, 1st gear of the T-5 is about 2.95 and 5th is pretty tall .68
so I 'm certain you could go 3.91 rear gear and maybe 4:11. (1st gear may wind up the rpms too quick with the 4:11, not sure). I'm sure someone with a T-5 will chime-in on that.

I have a different setup with the TKO-500 which has a 3.27 1st gear, so no "real world" help there.

ring-pinion.com has gear calculators and ddperformance.com has the t-5 gear ratios.

 

I can't believe nobody pointed this out so I have to do it since it is one of those things that just bugs me to death. If you want a highway gear that would be a high gear. If you want a drag racing rear that would be a LOW gear. The higher the number the lower the gear. Ratios are like fractions 1/4 is smaller than 1/3 even though the bottom number is bigger. 4.00:1 is lower than 3.00:1 even though the number is bigger. Get it?

 

I recommend 3.50-3.70 gears.

I have a T5 and 3.50 and think it is just about perfect.

 

I agree with the 3:50-3:70 suggestion. If this is primarily a street car you should be happy with those. If you are mainly racing with drag radials or slicks then 4:10s. As for an educated horspower guess. If it is on pump gas and not getting past 6000rpm by much then 325hp, with race gas and more rpm could be up to 375hp.

 

with a 5 speed trans id go with 3:50

 

It sounds like you're building a car for competition, in which case I will suggest that you gear the car to avoid having to upshift at an inconvenient time. Having a few mph left (but only a few, like less than 5) in 4th going through the traps or being able to pull 65 mph or so in second gear at autocross (depending on the lot) come to mind as examples.


Norm

 

My buddy had 4.56's with a t-5 and 26 tall tire and drives it regulalry on the freeway.it revs a little higher but nowhere bieng undrivable.If you have a street car, i would say between 4.11-4.56 from having driven a car with them and not guessing whiat "might" work.