Wheel speed calculations...

BluegrassDiesel

BluegrassDiesel

UK2K!
Joined
Apr 9, 2007
Messages
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Okay so help me out here and make sure Im doing this right, because im definitely not sure if i am:bang. Ive been sitting here doing some calculations partly out of curiosity/boredom and partly because im thinking of going to a bigger tire. So here it goes...

47RH/RE ratios
1st = 2.45:1
2nd = 1.45:1
3rd = 1:1
4th = .69:1

Transfer case ratios
4Hi = 1:1
4Lo = 2.72:1

Axle ratio = 3.54

So lets say just for example that I'm going down the track in 4Lo, 2nd gear @ 3000rpms

3000 / 1.45 = 2068.96
2068.96 / 2.72 = 760.64
760.64 / 3.54 = 214.87

So @ 3000rpm my tires are rotating at 214.87RPM

My tires are 265.75.16s which equals 31.64 inches tall. Meaning that the circumference of my tires is 99.39 inches

214.87RPM x 99.36 = 21349.48 inches traveled per minute
21349.48 x 60minutes = 12080968.8 inches traveled per hour
12080968.8 / 12 = 106747.4 feet traveled per hour
106747.4 / 5280 = 20.21

So when its all said and done, @ 3000rpm in 4Lo, 2nd gear with 265.75.16 tires, my tires are turning at 20.21mph???
 
If yuor math is correct and your convertor is locked then yes... simple way woud be to put in in 2nd gear 4lo floor it and watch the speedo...
 
Rods said:
Thats what I got usen this
http://www.snoman.com/HTML/axlecalc_5a.html
IMO you need more MPH mid to upper 20s
Click to expand...

Geez, I just used that calc and I was at 18mph with 3rd/4low - I thought at least 20...

If my math is correct, 2nd/4hi is next with 26-27mph - then 30mph for 4th/4low - Is this correct?

I cant imagine pulling in 4th(direct)/4low, ouch.

Dumb question :doh:: Are the 4hi gears more prone to break then the 4low gears?
 
I posted it elsewhere Josh but I have a spreadsheet I can send you to do this for you and you'll be able to see the wheel speed at various RPMs for each gear. It's a nice tool. If you want to see the change a tire size makes, simply change that setting in the spreadsheet and everything else changes for you. Pretty nice IMO.


C-ya
 
my question is this.....

which is better....

33's and 3.55's or 35's and 4.10's, truck is a 96 p-pump automatic......

cause i can get 33's in the tires i want to run, but i cant get the 35's in the width i want without going to another tire, would 4.10's kill the 33's off the line without letting me get any speed......


i plan on going to a 727 and a floater ford 205 with a ford high pinion dana 60 front axle some time next year.....so with the less gear in the t-case it should help alot instead of the 2.72 in the factory case with the 4.10's.....
 
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