I'm not trying to jump on anyone here, but the OP stated that it was "borderline unsafe". So are some of you people saying that a difference of 15 psi on the rear tires is going to cause a "borderline unsafe" drive condition? A solid axle, body-on-frame truck, capable of towing 11,000 lbs, 1500 lbs payload, go up Cliffhanger 2.0, and take on any number of situations is going to be severely hampered by 15 psi of tire pressure?
If you were telling me that it's tire pressure on a McLaren 675LT set up for max attack on the Nurburgring... fine. If you're running <25 psi on the street... ok. But 60 psi vs 45 psi on a truck designed to haul heavy loads down dirt roads, etc? Sorry, but saying this can all be solved by changing air pressure and no need to take it to the dealer to have it checked out is a little irresponsible. Please, drive the 100 miles and get it addressed. If I'm wrong... awesome. Happy to be wrong. But 15 psi of tire pressure difference should not degrade vehicle dynamics to an unsafe condition. Certainly not the case on my truck, which hauls my wife and kids every day.