Regearing the 2.5

[90growler]

I have read allot on how regearing the 2.5L can make a huge difference. Anybody have any experience with this or can you point me in the right direction? What am I looking for?:shock:

 

[Bounty__Hunter]

What gear ratio you change to depends a lot on:
Transmission type, manual or auto
Axle type
Tire size
Type of wheelin
Desired rpm at highway speeds

The 2.5L commonly has 3.73 gears with the auto and 4.11 with the 5spd. You can check the tag under two of the diff cover bolts to be sure. It'll be the 1st three digits.

If you're running 33" tires the best bet would be to swap to 4.88 axle gears, that's the lowest gear ratio that'll fit both stock axles. Anything lower to compensate for larger tires or for a lower crawl ratio would require heavier axles.

 

[90growler]

I want better highway and better acceleration. I have the dreaded AX-5 with everything else stock. Currently turning 31x10.5's and installing 1" body and 1" shackles. What would you reccomend? Do you need those #'s off the diffs?

 

[TwistedCU]

If you are not getting larger tires in the future then you may want to go with 4.56 gears. With 31" tires 4.88's would have your engine screaming on the highway and gas mileage will suffer greatly, although it would rock on a trail and be loads of fun to drive around town.

 

[ah_too_bad]

i recomend a throttle body spacer, k&n cold air intake. If you're only turning 31's there is no need to change out gears for highway use. and if you do venture above the 31's, go with full size axles, the dana 35 is prone to problems when turning 33's or higher. and if you are on a budget like most of us, just drive it like you stole it.

 

[Bounty__Hunter]

You likely have 4.11 gears, you can confirm with the axle tags. I too recommend keeping them 4.11 with 31" tires and doing a few simple power mods to the engine. I run the same setup, AX5 and 4.11 gears, with 33" tires. I can get out of my own way, it runs pretty strong after a cam and other mods. Regear to 4.88 if you plan on 33" down the road.

Why is the AX5 dreaded?

The 2.5L is generally easy on the stock axles, and generally okay for up to 33" tires. Don't think you HAVE to upgrade to heavier axles to run 33" tires.

 

[90growler]

I was actually thinking of running "32's. I ran those with everything stock on a "95 YJ I used to have. I have heard allot of negative things about the AX-5, thats why I said it was dreaded. I cannot do many other upgrades because I have the TBI Injection. So the cold air intake and throttle body spacer is out of the question. The motor runs strong through 3rd right now. I live in a hilly area and it is a pain chugging up and down the hills. I guess I will look to regear in the future. Any suggestions for how I could improve on top end speed without the gears, spacer, intake without spending a wad??

 

[Bounty__Hunter]

You can still do a conical K&N filter for a large improvement, along with the electric fan. Consider the 2spd fan from a 3.8L Ford Taurus, they're cheap and plentiful.

You could have a machine shop bore your throttle body and make a new butterfly valve. I've never looked closely at the tbi throttle body to see how much material can safely be removed.

 

[90growler]

OK, I am always talking about my throttle body injection and how much a royal pain it is, so I finally took a pictures of it. Does this help???