I have 3.55's, 32's & I pulled a trailer with 1600 lbs. on it & it did fine. I left it in "D" so I wouldn't get the trans too warm.

BTW, I have no sway bars.

 

I started on 33s with 3.55s. It sucks. You might not know it till you regear but you will notice it. Went to 34x10.50 swampers with 4.10s. Better than 33s with 3.55s but not good. Now running 31s and 4.10s. Trust me it will kick the **** out of 31s and 3.55s. I wheel mine, a lot, in the mountains. As some one stated earlier with my bumper , sliders and skid plates I have added a lot of weight. If you have a auto and are never going over 31s or 32s 4.10s will be great. You will notice a difference.

 

I ran 3.55 and 31a for a while.I was working at a copper mine and had to climb a crazy grade everyday for work.the Jeep really hated the hill climb with the 3.55, flat ground it was ok but no doubt about it the Jeep was not the same as stock.I switched to 4.11 and it was great.then jumped to 32a and now it's just like stock on the big climbs.basically if u drive most of the time on flat ground your gonna be fine.if u need to climb every day you will be better off with a gear swap.your Tranny will thank u

 

Exactly this ^, my MPG wasn't affected much I still get around 17mpg in the summer on backroads/town and get around 20 on the highway but keeping it at 65 on a steep grade kills it.