Q: Can issue with coupling in AWD SUV cause an oil leak of the rear main seal? Only 60K miles 3.5 yr old car

The term "rear main seal" normally refers to the crankshaft rear main oil seal. If that is the seal you are referring to, improper towing would have zero effect on that seal. Furthermore, if that is the seal you are referring to, it is exceptionally unusual for that seal to fail on such a new car. The rear main seal is very robust and quite unlike the front crankshaft seal which predictably fails after 6-8 years. If you are referring to transmission seals, those seals seal rotating shafts. It doesn’t matter if the shaft is supposed to be turning or not; if the shaft turns, as a consequence of improper towing, the seal still works the same way and so improper towing is irrelevant. The only conceivable failure mode of the seal is overheating of the unit which would damage the rubber in the seal and where such overheating was a consequence of the improper towing. Depending on the required repairs, it will be cheaper to have them performed on a mobile basis. If you want to consider that option, to obtain a conclusive diagnostic and an estimate please request an estimate. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.