Gear ratio questions....

[Flaren]

Ok, I'll just say right up fron that I'm basically an idiot when it comes to most technical stuff associated with cars in general nevermind a KJ. I'm curious about how a gear ratio works and what the numbers really mean. According to Jeep.com:

"A numerically lower axle ratio results in lower engine rpm and better fuel economy. A numerically higher ratio improves acceleration, climbing grades, carrying loads or pulling a trailer. "

If that's so, then I guess my question would be why is the Renegade on the low end at 3.55?I kinda thought from the information that it should be the other way around maybe? Do the higher ratios for the Limited and Sport translate into better on-road performance? Does a lower one make the Renny a better off-roader? Is there a specific benefit to this gearing? Sorry, the knowledge-thirsty geek in me gets loose from its cage at times....lol. 8-[ Thanks all!

(P.S. If I posted this in the wrong place, could one of you lovely mods move it for me? Thanks! #-o )

 

[grogiefrog]

Flaren, good question! =D>

The Renny's 3.55 means that it requires 3.55 turns of the driveshaft to achieve 1 full rotation of the tires. As said, the lower ratio provides slower acceleration. The idea is, you want a lower gear for trail use vs. street use (which is where the Renny is marketed). Lower gears are usually best for sand and crawling, and sometimes better for mud and loose hill climbing where you want low end "grunt".

A higher ratio helps for pulling a trailer for example, where it allows a few more engine RMP's and therefore the engine handles the weight and drag of a trailer better, and of course brings down the MPG.

 

[Flaren]

Thanks grogie! Makes sense to my head now! (My inner geek thanks you...hehe.)

 

[JeepJeepster]

Ur right grogiefrog except for that last part about pulling a trailer. A lower gear would also help for that, a lower gear brings ur rpms up, just think, a 3.73 means the drive shaft has to turn more to get to the same place. That means the engine is turning faster to make u get to the same place. Its kind of confusing, a 4.10 is a lower gear than a 3.55. So i really have no idea y they put a higher gear in the rennys. I guess they are tring to get the mpg's back up with all the extra weight from the skids and light bar and everything.

 

[Eddo]

3.55 is only for the 6 speed. Look at the gear ratios in the transmission and you will see why there is a need for 3.55 gears. Something like 4.41 first and .86 OD.

 

[grogiefrog]

I stand corrected... thanks Jeepster. Right, lower! #-o And makes sense about the extra weight to bring back up the MPG.