Gear ratio or not........

[rollbar]

O.K. some thing interesting was mentioned to me today when I was talking to a friend of mine & we were talking about gears & re-gearing.

I told him & showed him w/33" tires & a 2.73 gear ratio that it would be nessessary to regear, correct.

Hears the answer I got, No I don't.

I comenced to tell him all my knowledge of gear ratio's w/tire ratio's etc. & showed the charts to him etc.

He said the he just bought the Jeepers bible & it states in there (which he still has to show me) that you can get the samething by changing the cam out for more torque & that I wouldn't have to regear.

I said I understand & agree to a certian extent but would still have to regear.

So what do U say, is it the same answer as I gave due to our teaching & the calculations of ,

New tire size
-----------------============% of change x original gear ratio = New gear ratio.
Stock tire size


So how bout it,

RollBar

I didn't mention if it was a auto or manual tranny.

[Trailbst]

Six to one, half dozen to the other.

If you think about it, you both are correct.

We change our gearing to keep the same type of engine output as stock. If you want the engine output to feel stock with bigger tires and stock gearing, then you increase the engine performance to make it feel stock.

Two ways to look at it, that's all.

For example, how many trucks do you see in the mags with 44" Swampers and they are running 4.10s or something "high" like that? They can get away with it because they are running big V-8 mills with lots of horsepower and torque.

Now imagine if they regeared and were able to put more power to the ground through better gearing. The truck would feel faster and more powerful than stock.

You're both right. Achieving a stock feeling output from the eingine.


Erik

[Goose]

I have always felt that dropping the gear ratio reduces the load on the driveline. big tires simulates big load. Which means if you have the additional power to move the truck like stock the load is on those ujoints and tranny t/case .. this is not a reasoned scientific opinion just a gut feeling kinda thing.

on the flip side I have always figured that since I do most of my wheeling in low range.. I don't go as low as some guys will 3:73 with 33's since It slows the RPM down at highway speeds I pick up a little fuel mileage and still have low range to play in.

[Mudrat]

Based on the Auto-Math handbook, I made up a little Excel sheet that you can plug your variables into and get engine RPM for tires size and speed. You need to input some data, but it's self explanatory.
If anybody want's it, it's an Excel spreadsheet you can download and use from HERE (http://members.cox.net/b-ballangel/RPM%20-%20Grears.xls)

Mudrat

[rollbar]

Cool thanks,