Hey guys, got a question I haven't found answered.

What is the negative about regearing? Is top speed limited? Hurt the engine? Force higher RPMs and shorten engine life?

I know power and gas mileage improve, but what's the catch? Like someone told me NOT to get 5.13s and only go to 4.88 since it's my daily driver(now on 35s). I'm confused what the drawback is?

 

Just the high RPM's which bring down gas millage. Thats it. I have 5.13 power is good, gas millage is bad, it will cruise at 80 sometimes more. So biggest draw back is gas, if its a DD then you might want 4.88's for gas and still have the stock power, if your not going to complain about gas then go the 5.13's. thats all.

 

I thought gas mileage improves with regearing?

 

I'd say that about sums it up.
You are not going to harm your engine by re-gearing, if anything you are going to help it by reducing driveline stress from the larger tires your already running, it's going to be alot easier for your engine to turn those axles and tires, just at a higher RPM...and in my opinion, your making more effective use of the 3.8L power band this way...all while reducing stress on driveline components. Keep in mind I base this opinion relative to your tire size and proposed gear selection

 

NO. Depending on what gears you get the worse the millage.

Gears just give you stock engine and execration performance, not gas millage.

the higher the gear the worse themillage, 3.21, good, 5.38's very bad.

so 4.88's will get better MPG than 5.13's, but worse than 4.10 and 3.73 will get better MPG's than 4.10's. So no matter what, you will loose MPG, just how many is up to your gearing.

 

I've read that people reported gas mileage going back up after regearing... I guess they were mistaken.

Thanks for the info!

 

Remember, this is with a 6 speed. With an auto and 35's, 5.13's will up your mileage. Not by much mind you, about 1.5 mpg or so, but boy does the Jeep perform much better.

 

I went up about 2mpg , after rearing to 5.13, 35's, auto.

 

Smaller pinion gear - maybe a bit weaker. Haven't found any posts of anyone breaking one yet.

Gas mileage will generally go down - that's why the factory trys to get away with as highest gear (numerically lower) as possible.

Top speed is limited, but only by the amount you overgear. I have 5.13's, 35" tires, and an auto transmission and don't like the way the engine revs at 75 MPH. That's OK though since the low end really makes up for it.

The dealer warranted my transmission. I tow a 3500# trailer. He said that if I had the 35's and the stock gears (4.10's - it's a Rubi), it could have been a hard sell on the warranty. However, since I had upgraded to 5.13's he said that helped make a case!

So, if you like to go really fast or expect real high gas mileage, 5.13's aren't the right answer. However, if you like the low-end improvements and don't mind slowing down a bit - go for it!

 

So, I'm getting like 12 mpg local when I used to get 16. Since I have a 6-spd with 4.10s, it will go down even more when I upgrade to 4.88?