[93mustang]

I'm having a rear gear change done because my car is a dog out of the hole drag racing with the T-5z's 2.95 1st gear.
It's use to launch great with my old T-5 with a 3.35 1st gear and 3.73 rears.
But now it bogs and takes some time to wind up, even at 5k plus launches.
Does anyone here have a T-5z that they drag race with?
Just wondering what rear gear to go with.
I'm debating between 4.10's and 4.30's. I'd like to go with the 4.10's, but I don't know if that would wake it up enough, and then I'd have to pay for another gear swap for the 4.30's.

My average trap speed in the 1/4 mile is anywhere between 102 and 105 mph with the 3.73's depending on conditions and wind direction.
I used a gear ratio calculator and this is what I got for a trap rpm.

4.10's @102mph=5400rpms
4.10's @104mph=5500rpms
4.30's @102mph=5650rpms
4.30's @104mph=5758rpms

Also did a final ratio comparison for 1st gear.
My old T-5 with 3.35 1st gear and 3.73's =12.50
My new T-5z with 2.95 1st gear and 4.30's=12.69
My new T-5z with 2.95 1st gear and 4.10's=12.10

Current set up is T-5z with 2.95 1st gear and 3.73's=11.00

So I'm either at .40 under or .19 over my old set up that worked well.
I'm really leaning towards the 4.30's

Any suggestions would be great!
Thanks!


1993 GT Mustang / Ford Racing GT-40 Crate Motor B-303 Cam / 24 lb. Injectors / Stock Ignition / MSD EFI Blaster Coil / Edelbrock 5.0 Upper and Lower Intake with BBK Phelonic Spacer / Professional Products 70mm Throttle Body / C&L C.A.I. w/76mm MAF / Stock Air Box w/K&N Panel Filter / Holley Adjustable Fuel Pressure Regulator / Electric Fan / BBK Underdrive Pulley's / A.C. Removed / BBK Short Headers / Flowmaster Exhaust / Tremec T-5Z / B&M Short Throw Shifter / Alum. Driveshaft / 3.73 Gears / Eaton H.D. Posi / Moser 31 Spline Axles/ Subframe Connectors / Line Lock / Driveshaft Loop / B&M Short Throw Shifter / BMR Upper and Lower Control Arms / Lakewood Adjustable Drag Shocks/ Holley 190 lph Fuel Pump /

[EagleAutosports]

Looks like you've done your homework, great way to figure those numbers out.
Stepping up to a 4:10 would make it run the way you want, that's what I'd go with. Is this a weekend play toy or a daily driver?

[93mustang]

Not a dailey driver.
Street legal, some short drives, drag raced mainly.

[StalkerStang]

I ran a T5Z with 3.73's and it worked out well. Launched off my rev limiter though (6500 rpm). Best 60 ft. in the 1.7's and trap anywhere from 104-109 mph depedning on weather (it gets very hot in Phoenix).

[93mustang]

Originally Posted by StalkerStang

I ran a T5Z with 3.73's and it worked out well. Launched off my rev limiter though (6500 rpm). Best 60 ft. in the 1.7's and trap anywhere from 104-109 mph depedning on weather (it gets very hot in Phoenix).

With my old 5.0 motor at about 245 hp, 3.35 1st gear, 3.73 rears and drag radials (Nittos) launching at 3500 I got 1.8 60'.
I'm launching this new set up, (T-5z 1.95 1st gear with 3.73's, 345hp Ford Racing Crate Motor at 4000 to 5500 and it hooks and then bogs. So I'd rather go with a different rear gear and lower my launch.
And I really don't want to launch at 6500!!! Wow!

[StalkerStang]

Yeah launching at 6500 was a bit nerv wracking at first, but its no different than launching a big block right in it's torque band, no matter what the rpm, the ideal launch point is probably whats also the right rpm to break stuff. (which I have lol).

[RLG34750]

Are you on slicks or street tires.....

[93mustang]

Originally Posted by rlg34750

Are you on slicks or street tires.....

Slicks
15x9.5 Hoosier Quick Time Pros

[RLG34750]

Originally Posted by 93mustang

Slicks
15x9.5 Hoosier Quick Time Pros

before i'd change the rear

try a taller tire and play with your air pressure