Thanks, all. It turns out that an internal pump in the transmission failed. It had nothing to do with towing. Even though it is out of warranty, Chrysler stepped up to pay 75% of the repair/ rebuild cost. I wish I didn't have to pay anything, but I must say I am impressed with Chrysler/Jeep in this circumstance. Now I'm thinking about that gorgeous 2011 Grand Cherokee on the showroom floor...