Rear

Hi all. I just recived a 05 silverado crew cab with the Light Duty Power Package.(5.3 tow package locking Differential ect) My 1st chevy in a long time. (no more gas guzzling bad handling fords) I drove it from Maryland to Tennessee (doing 75 or so) and got 23mpg,and was very happy with the truck. Then I took it camping a few hrs away to western Maryland towing my 21'

4500 lb camper and was not happy at all. It has a 3.23 rear in it and I thought its way to high to tow the camper. The outside tem gauge said 96-101 while driving in a 30-40 mile bumper to bumper mess.When the road would open up going up the mountains it would really have a hard time. When I got to the campground I could smell the breaks. I put in a new prodigy brake controller and must not have had it adjusted right. (Buts that's a whole different story) On the return trip I had open road lower temps a well adjusted brake controller and had much better luck. So was it the temp or did the fact I got a good running start up the hills help? I was wondering if anyone has the same set up and how well they do towing. I was also wondering how much do you think it would it would run me to change the rear(I guess to something like a 3.73?) and what that would do to the warranty