I have a 97 Wrangler, 4.0 Automatic (3 speed),,I recently added a 4 inch Rough Country Suspension lift and finally purchased a set of 285/75-16 Firestone M/T Tires along with Granite Alloy wheels. I have noticed a dramatic decrease in performance and fuel efficency,,I took a short trip to Dodge City last weekend and with a 20 mph headwind I could barely keep a constant 60 mph (using GPS, not speedometer to measure),,,the transmission constantly wanted to downshift if I barely increased the throttle,,I had a full tank of fuel when I left home and filled up in Dodge to check my fuel consumption during the drive,,,I had driven 60 miles and it took 5.8 gallons to fill back up.
My question is,,can I find out the current gear ratio by checking the tags on the rear end,,,,what would be the highest gear ratio suggested for this vehicle considering that it gets more around town and highway driving than it does full blown 4wheeling. I use my Jeep as a semi-daily driver.
Also, if my ratio is numerically lower than 3:73 (I'm guessing it is),,it looks like from the catalogs that I will have to change the carriers along with the ring and pinions,,,,true/false????
My Jeep is in good running condition but stone stock besides a cat-back exhaust,,,should I put my money toward performance mods,,headers, full exhaust upgrade,,performance computer chip/module,,etc,,,instead????

Thanks for any suggestions,,tips,,  

You definitely need to re-gear. To restore your original performance you need 4.56 gears. To get a little more performance than stock, 4.88.

While you're in there, consider some traction devices. You'll need new diff carriers anyway.

Don't waste the money on exhaust, chips and cold air systems.

They are not of much benefit to you whithout other internal engine changes. They just tune your engine to run on premium fuel and increase power slightly in the upper RPM range. Not where you need it, down low. And you'll see a drop in overall fuel economy.  

well...  actually with the three speed 3.73's are good for the 285, I personally wouldn't go beyond a 4.10 unless it does very little daily driving duties.

if it had a 4spd OD ftgiles is exactly right on the money there.

the darn thing probably has 3.08 gears in it. 3.73's will go on the carrier ya already have.

the 3.73's will run down the road @60mph about 2300rpm with the 32.8" tall 285x75-16's  

WHAT? It has a 3 speed. Sell it!

Sorry, missed that detail. I had 4.10s in a YJ 3spd with 32s. I liked it ok. Got 10 mpg on the hi way though.  

yeah! I figured cause ya don't usually miss that stuff...  

Thanks for the input,,,and yeah I was pretty sure I should go with 3.73 gearing,,,but seeings as how I'm really new to Jeeping,,I wanted to get some expert opinions. It bites to sink money into something that you are "pretty sure of" only to find out you were off the mark. THANKS AGAIN GUYS!!!