We spent several months at Boyce-Thompson Arboretum, east of Apache Junction, AZ, where they have a major issue with those critters. What they had use do was to keep lights under the RV at the engine and also under the genset. Other places help as well. What we did was to get a couple of strings of the clear, small Christmas lights and place them around under the motorhome, about 2 feet inside of the drip-line around the RV. I put them on one of the dusk to dawn light sensors so that the came on each evening and off at daylight each day. There were seven couples who wintered there and we had a lot of pack-rat activity in the area yet not one of us had any problems with them around our RVs. I really think that this is a good answer.
And to keep them out of your towd or tow truck, you can put a light under the hood, or just leave the hood up at night.