rear end ratio
 

I have a 2000 F150 HD, 5.4L, the existing rear end ratio is (I believe) 3.73 which was part of a tow package, I only use the truck to tow a 5th wheel camper and rarely drive much more than a few miles a week other than towing the camper, want to be able to go up the hills better, so my question is, Is there a better ratio available for that F150. 4.25 or something ?? also would I need to get a new (or used) axel in that ratio or are the gears changeable.

You can get 4.10, 4.30 (if 2WD), 4.56, 4.88, or 5.13 as a direct swap of the ring and pinion without changing carriers.

4.56's would be the best choice.

Thanks, 4,56 it is. it is a 2WD, was working on my camper and getting it and the truck ready for a early spring / late winter trip to the gulf. I noticed a tad bit of oil stain where the drive shaft enters the rear end (rear end front seal sounds about like what it is) I guess if I am going to swap out the gears might as well change all 3 seals, (front, left and right) will I need to adjust the speedo ??

Yes, you will need a programmer. Custom tunes will be well worth it for other performance enhancements.

Your speedo will be off a ton (like 30 mph), so you will need to adjust that.

What size tires are you running? I'd consider 4.30s depending on the size. But you don't use your truck very much, so 4.56 is a solid choice.

My 4.88 gears and 35" tires can chug straight up a huge incline with cruise on, locked in OD, and not break a sweat, but the RPMs are pretty darn high.