Gearing

PACougar

Active member
Jun 27, 2012
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Mika, I think you would be fine with 3.42 as long as you run at least a 32 inch tire. What kind of RPM are you looking at turning by the end of the run?
 

Mika

Bastardo Finlandias
Oct 25, 2008
291
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Finland
i had around 3800 rpm in finish line at 138 mph in quarter. But it was with slicks, my street tires are smaller in diameter.
I would like to keep engine rpm under 4000 in line at mile.
 

PACougar

Active member
Jun 27, 2012
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I think you need to decide on a tire height to really make up your mind on gearing. 32" tire 4000 RPM you're doing 157 mph, put on a 35" tire and you'll top out at 172 mph. I know your truck has a lot more than 157 in it, so you'll either need a really tall tire or have you considered a 6 speed valve body upgrade? If you had the 6th gear you'd be able to hit 180 mph at 4K with 32" tires.
 

Mika

Bastardo Finlandias
Oct 25, 2008
291
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Finland
I have Duraflite, not Allison so 6-speed it out of question.
But how is it with gear vendor, it will give needed gearing?
 

PACougar

Active member
Jun 27, 2012
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Just got done looking it up:) I would be weary of the gear vendors unit holding the power, but I'm no expert on their products. Do you know what size tire you are going to run? I think if you run a 32" tire you still might be ok as is. .69 bumps you to 161 mph and if you're willing to turn a little more 4250 get's you to 172 mph.
 

McRat

Diesel Hotrodder
Aug 2, 2006
11,249
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Norco CA
www.mcratracing.com
I put a Ford 9" axle under the back of Casper for the second year. 2.50:1 gears are cheap.

But it would go over 175 mph with 3.42's and Allison.

Toyo Proxies are 18" rim, speed rated at 32.4" diameter. Those are what I first used. Later I ran specialty tires.
 

COMP461

Diesel Pro
Apr 29, 2008
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Aledo Texas
there are many calculators apps on any phone.
The gear vendors is bullet proof .
If you going to go Mile racing it is a cross between Drag racing and LSR. I went 167.88 with Diesel Powers Project X diesel using a nine inch ford and 3.20 rear gears with a Gear vendors


the toyo Proxies are good times I use the 245 45 20's on X and it worked well. I would never advise a tall 4X4 tire, too much side wall, and if you blow a tire your dead.

you are required to have a speed rated tire at all of the mile events


here is the tire and wheel combo


PICT0042JPGProjectX.jpg




PICT0005JPG163mph.jpg
 

RPM Motorsports

smokinum
May 13, 2008
3,271
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Central Valley Ca.
We are currently beating the crap out of a GV unit, no issues so far. We do have the race version GV as a backup if the standard fails. We keep tabs on the fluid, and change it every other pass.
 

COMP461

Diesel Pro
Apr 29, 2008
429
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Aledo Texas
I use to go the other way , on gearing with the GV unit on gearing . In project X I ran a 4.56 or 4.88 rear gear with a 28 tall tire . it was good for 1.6's 60 foot every time
 

PACougar

Active member
Jun 27, 2012
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I know my truck with 3.42 and 305/50R20 at 4700rpms in 5th gear is 162mph! I would love to do the standing mile in my truck!:thumb:

Mark, I think you'd run out of RPM's in the mile, your truck wouldn't have a problem finding 162! You need to find yourself a 1/2 mile event and go show some exotics what a fast truck looks like. Plus there's a lot lower chance of blowing up in the 1/2 mile.