Again, if you're going to tow with your current rig, keep an eye on that rear axle. I broke mine twice with numbers similar to yours.
On long drives, whenever we stopped, I'd crawl under the truck and feel the rear axle housing. A digital/infrared thermometer might be a good $30 investment. Make sure it's not getting too hot. We actually did some overnight driving so that the cooler temps would help keep the axle running cooler.
Getting a rear diff cover with the cooling fins is a really good idea. Increasing the frequency of axle fluid changes probably isn't a bad idea either.
