i have a 98 cherokee with 4.0 on 33's with a five speed and 3.07 gears getting about 10 mpg
i have 3.55 geared axles and was wondering how big of a difference it would be if i swapped them or what my mpg would be like
thanks

 

If you've got an AX15 go right ahead and get 4.11s or 4.56s. It should help. Check all of the normal bad MPG stuff to make sure everything's sound.

 

The 3.55s won't be enough.

 

Depending on whether you are more partial to city/off-road or highway driving. To keep the closest gearing to stock, go with the 4.11 gearing. You will still have crappy city milleage because of your long gears, but your highway should improve markedly. 4.56 gears on the other hand will make your gears "shorter" and make it easier on the engine to accerate the vehicle. This puts your overdrive at a lower speed for optimal highway cruising, so to go 80, you would be bringing your vehicle out of it's factory tuned optimal area, hence use more gas on the highway, but you'd use less in the city. I put some more interesting tidbits in this thread:

https://www.cherokeeforum.com/f59/ga...erokee-127572/

Hope this helps.

 

i guess what im trying to ask is with a 5 speed on 33's how big is the difference between 3.07 and 3.5
ave 3.55 axles so it would be a free swap

has anyone ever used rough country gear sets? and is it an easy swap?
thanks
http://www.roughcountry.com/gears/jeep-xj.html

 

Swapping gears is a challenge. If you dont have patience, it wont go well.

3.55s won't be enough.

 

Just to add my two cents I have 33's and 3.55's as of now 16 mpg highway every trip and a little less in town although I have never figured it. Going up to 4.10's soon with 35's should be good enough for me. Have gotten along well with the stock gears so far but I will find out if I like the 4.10's when I start wheeling more than I ever have this summer.

 

Your two cents is skewed because the OP is asking about the manual trans, not the automatic.