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What can I do to get my performance back?

Article written by MJ Staff

Date Added: 06/23/2008

Here at MOABJEEPER Magazine we often get email questions about regaining performance, and ever increasingly, gas mileage.

This question arises from the underestimated massive power sucking ability of large tires. And if you have ever picked up a wheeling magazine there are a lot of aftermarket modifications claiming all kinds of power gains, but to cut to the chase, there is only one way to gain both performance and gas mileage? regearing.

We could of course spew out a bunch of numbers to explain this, but that tends to hurt the brain and it could be explained so much easier. Your stock rig came with some pretty small tires and gearing to match your engines power output. Since we already said we hate to make our brains hurt, imagine that you?re pushing a 1970?s little 1806lb VW Bug. If you haven?t actually pushed one; it?s really pretty easy. This represents your stock Jeep.

Surely though you haven?t left your Jeep stock. Now you have these large tires that your stock engine and gearing are straining to push. Actually those big tires you?re running are probably about twice as hard for your engine to turn. Now imagine that Bug in our demonstration is a fully loaded 4000 lb SUV. The load has at least doubled, and you are still standing there by yourself trying to move it. It won?t take you long to realize that having a friend behind that SUV would be a huge help and get the load close to the ideal stock form (in our human guinea pig demonstration) of about 1800 lbs per human. This is essentially what happens when you regear your Jeep.

You may have noticed we said ABOUT as easily. We know that 1800 lbs is ideal for one human, and the mathematically closest ratio on our 4000 lb SUV is two humans (pushing 2000 lb each). This ratio is as close to stock as we can get, and thus about as close to stock MPG as we?re going to get; however, you will still sacrifice a little bit of performance from the stock ratio because each human is pushing 200 lb more than stock.

Back to your Jeep. If you punch in the gear and tires size numbers on any ole gear calculator it will give you the closest mathematical match to your stock gear ratio. The problem is the calculator only considers tire diameter and does not account for additional weight of the tires. So while you may be mathematically correct in terms of height, you simply don?t have the extra power to push the added weight.

Lets go back to human guinea pigs again. What if another buddy came along to help push? Now the three of you can push this SUV around quite easily. This is similar to picking a numerically higher gear ratio than what would be the stock equivalent (also known as lower gears. Yes it?s confusing. Higher number = lower gears). Ex. If the gear ratio calculator says that 4.10 : 1 gears are stock equivalent for your particular tires, 4.56 : 1 or 4.88 : 1 would be like adding that third or even fourth person and dramatically improve your performance. The down side is that generally you will get a reduction in MPG if you go that extra step with the gearing. For some people (all of the MJ Staff), the extra performance on and off road is worth the dip in fuel economy, but if you?re more concerned about getting the most out of every drop of gas, you?ll probably want to shoot for the closest stock equivalent. There is no correct or incorrect configuration. It comes down to priorities and preference.

Of course, there are always those with automatic transmissions who will tell you, ?I went to a larger tire size and hardly noticed any difference.? The reason they don?t notice a drop in performance is that automatics hide what is actually going on unlike a manual transmission. If we peeked inside the transmission, you would see the transmission belts are slipping more than they should to try and maintain stock performance. End result, the transmission wears our long before it should have. Furthermore once those people actually do regear, they discover there really is a significant difference in power and mileage.

Final Thoughts

Obviously You?re not going to get 2x the power out of your Jeep by simply regearing it. This is just an analogy to illustrate the concept of why your Jeep is straining so hard and what a gear change will do for you.

As to those performance parts we made reference to at the beginning of this article. Some of the aftermarket products available will give additional performance, but none of them will correct for an improperly configured drivetrain.

If you are considering regearing, and want to play around and see how far off your speedometer is or what gears you should be running, you can visit a super secret web page here at MOABJEEPER Magazine.

Super Secret Gear Calculators

If you?re still not convinced about the benefits of proper gearing, find one person in your local 4 wheel drive club and ask them how much of a difference it made and if they would do it again.



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