Steve,
I may be misunderstanding the situation, but if you are talking about smelling something when driving it after towing it for 3 hours it might be the smell of the accumlated road debris (mostly rubber) that collects on top of your exhaust system while the vehicle is being towed, and then gives off an odor due to the very hot exhaust system.
If not, it could be the smell due to a parking brake that may have been left on a little.
I know a guy that left the parking brake all the way on and in a few seconds there was the smell of burning rubber.