Since I'm out for the rest of this season, I figured I'd get started on changes for next season, and first thing on the list is gearing/tires. Which option below would you go with if it was you. Keep in mind that I'm working with approx. 675-700HP, C6, and 33 or 35" BFG All Terrain's. Calculations are with 35" tires.

Trans Xfer Ring Final Wheel speed
gear gear Ratio
1. 2.46 - 1.98 - 5.38 26.21 = 27.8mph
2. 2.71 - 1.98 - 5.38 28.87 = 25.3mph
3. 2.71 - 1.98 - 5.13 27.53 = 26.5mph
4. 2.46 - 1.98 - 5.13 24.99 = 29.2mph

If you have another suggestion other than going manual (no $$ for that yet), I'm all ears. 2.46 is the standard C6 first gear, and 2.71 is a C6 with E4OD gears (I think that's possible). My goal is more wheel speed, but I don't want the ratio down to where I run out of motor.

Sorry, The spreadsheet I have listed the 205 low as 1.98, but a little research on the 'net shows that it is 1.96, so here are the correct numbers.

Trans Xfer Ring Final Wheel speed
gear gear Ratio
1. 2.46 - 1.96 - 5.38 25.94 = 28.1mph
2. 2.71 - 1.96 - 5.38 28.58 = 25.5mph
3. 2.71 - 1.96 - 5.13 27.25 = 26.75mph
4. 2.46 - 1.96 - 5.13 24.74 = 29.5mph

If I use 33" tires the results are as follows.

Trans Xfer Ring Final Wheel speed
gear gear Ratio
1. 2.46 - 1.96 - 5.38 25.94 = 26.5mph
2. 2.71 - 1.96 - 5.38 28.58 = 24.05mph
3. 2.71 - 1.96 - 5.13 27.25 = 25.2mph
4. 2.46 - 1.96 - 5.13 24.74 = 27.8mph

something is not right with your figures.
Please post your formula.
Without a way to verify your figures, meanin yur mph, and knowin the formula I use, you would need about 9000 rpm with a 5:13 + gear to get 29 mph.
Thanx

Shoot me your email address and I'll send you the spreadsheet (if you have Excel)
The formula it uses is as follows;
Tire Rev = Tire Dia. x 3.14159/12
Axle rpm = engine rpm/overall gear
Overall gear = tranny gear x Xfer Case gear x Axle gear

Final tire speed formula is
Axle rpm x tire rev x 60/5280

(rpm x Tire diameter)/(total gear ratio x 336) = MPH

[(MPH x total gear ratio)/Tire diameter] x 336 = rpm

If my formula for total gear is correct (tranny gear x tcase gear x axle gear) then my mph formula is within .01 mph of yours.

Shoot for what ever will give you 29 to 31 Mph. wheel speed.



ShaZam

I was wondering what the wheel speed difference was between 2 trucks geared the same. One with 35" tires, engine rpm 6700 and the other truck turning 7200 rpms with 33" tires.
I don't know the gear ratio in the trans& t. case. But both are the same year model fords. 78/79 with 4.10 rearend gears. I am pretty sure they both have the same trans.

According to my calculator, if everything else is the same, then the trucks will have the same wheel speed.

Thanks for the info. I am trying to compare my truck. the one that runs 6700 rpm to another guys truck that turns in the neighbor hood of 7200.
That will give me some other things to look at.