What gear ratio would you pick?

[Mock4147]

I just installed the new vmp gen IIR on my 1967 f100 truck with a 2007 gt500 engine and trans. Working on the tuning with vmp now as soon as it is done I would like to change out my rear end gear ratio. The truck has a IRS out of a 2004 mustang cobra when I bought the IRS it had 4:10 gears but what I don't like is at 75mph on the freeway it is at 3400rmp in 5th so I want to shift in to 6th and when I do the rpms are at 1900. I will be driving the truck mostly as a daily driver in the summer month and going to track 1-2 time a month to have some fun. I was wondering if I should go with 3:73 or 3:55 gears


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[PaxtonShelby]

We need pics please...

 

[Mock4147]

We need pics please...

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[PaxtonShelby]

Great looking pickup right there. Two thumbs up on the drivetrain choice!

The gear ratio you end up with depends on where you'll end up HP wise and if you are able to put it to the ground. Plans to mini tub? Wider rear wheels and more tire? I would consider 3.31's to make it a great cruiser and make it easier to hook. I picked up a set of 3.31's for my '14 GT just in case I end up going FI or CJ intake/E85 someday. Car is tough to hook at stock power levels.

 

[Mock4147]

Great looking pickup right there. Two thumbs up on the drivetrain choice!

The gear ratio you end up with depends on where you'll end up HP wise and if you are able to put it to the ground. Plans to mini tub? Wider rear wheels and more tire? I would consider 3.31's to make it a great cruiser and make it easier to hook. I picked up a set of 3.31's for my '14 GT just in case I end up going FI or CJ intake/E85 someday. Car is tough to hook at stock power levels.

I hope the hp numbers are around 750-800rwhp I am having vmp do two tones on for 93 and one for e85 I am hoping to get 12" wide rims in the back with 345's and 10" up front thinking either Mickey Thompson et street s/s or toyo proxes r888r in the rear


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[Catmonkey]

What's wrong with using 6th gear? What's the rear tire diameter?

 

[nxhappy]

if 410s are too much, move down to 373

 

[Catmonkey]

Based on what you posted on speeds and rpm ranges, you're not far off from the stock gearing with stock tires. I'm guessing your tires are taller and taming your current axle ratio.

 

[RedVenom48]

Honestly, 1900 in 6th at 75 is pretty damn good. Ive got 3.73 with my 6th at .5 ratio and im juuuuust at 1900 from 75-80. Thats with 27" street tires too.

With my old VMP tune and TVS at the time i got 20mpg on the freeway with 3.73s. My 1st gear is a rowdy 2.97:1 so she moves out with the 3.73s.

Stick with the 4.10s and cruise at 75. Rape everything all other times with that set up.

 

[Mock4147]

I plan on going with Mickey Thompson et street s/s 345/35r18 in the rear and Mickey Thompson street comps 275/40/18 upfront


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[Catmonkey]

MT advertises a 27.8" diameter, so 3.55 would get you close to how these cars were geared from the factory. The 07-12 transmissions have a fairly short first gear ratio, and the 11-12 SVTPP had only a slightly shorter tire with 3.73s with that same first gear ratio. The earlier transmissions had a lower fifth and sixth gear ratios.

 

[xblitzkriegx]

save your money, keep the 4.10.

 

[Jam421]

I agree to keep the 410's ....decide later if that's a possible goal. The GT500 engine makes plenty of TQ to cruise at 1900rpm. Since the motor was originally designed to perform at that rpm while cruising with 331's it's actually working way less to keep your highway speed through the 410's. Besides...as also suggested above the tall tire you are planning is about 1.75" taller than what the GT500 motor/trans were designed around. This will effectively drop your rear gear ratio to around 3.90. Why not get the MT's ....go out and play...test them out for fun....run thru the gears...try a short highway cruise then decide on change. When you change tires it's a good idea to flash your computer with that tire size & gear for more accurate mph & rpm's.

 

[Catmonkey]

With tire size he stated, at 38 mph, he'll be on the rev limiter in first gear with 4.10s. He could get all the way up to 44 mph in first with the 13-14 first gear.