Re: 05 Escape PTO/transfer case issue
I'd get another diagnostic. These transmissions don't have 'PTO'. The transfer case mounts on the end of the transmission and then the transfer case directs power to either axle as it sees fit.
At 60K you should have changed the transfer case fluid at least once. It doesn't hold much fluid, and has to be changed regularly (every 30K - that's when I change my Tcase fluid). It should state all fluid changes in the owners manual.
If you've always taken the vehicle for service at the dealer, I'd question them about this, as if they overlooked a fluid change, that you might have even paid for but they never did it (techs forget just as often as the rest of us when filling out paper work).
AWD transfer cases have a centre differential to allow some wheel slip while driving on pavement, so the axles don't bind up. As long as you don't 'lock' the system it shouldn't cause any problems. The computer controlled AWD cars, such as AUDI for example, are a riot once one tire wears faster than the others, as the only solution is to replace all four, or you'll have massive ABS and drive-ability problems. The tire with the least amount of traction will spin regularly and burn out the clutch pack faster. Ford's system isn't this advanced to notice. You could easily run tires that are up to 1" larger or smaller in diameter on either axle, just as long as you don't lock the system together while on pavement (very loose surfaces only!). If you look more closely, the spare tire is actually smaller than the regular road tire. Obviously manufacturers wouldn't use a smaller tire if the driver was expected to easily put 100miles or more on it.
You are right in making sure the tires are properly rotated and at the same pressure (a decrease of 10psi can shorten a tire by up to 0.5" depending on side/load capacity). Most transfer cases are overbuilt for the job they were designed for. I'm sure the Escape transfer case could easily be bolted up to a high torque V8 engine and last forever. As an example, the one in my Durango (Dodge) can safely handle up to 1400lb ft of torque. The one in my old GMC K1500 could handle 1200lb ft from the factory.
If anything, take the vehicle to another shop, or two, for another opinion on the matter. Axle (gears in the differential case) have a tendency to whine if they're about to go. I would imagine the Escape has a rear pinion of sorts, that might even be the culprit. My E-250 work van had a gear whine at only 54,000kms (31K), turned out the pinion was so badly worn, the ring gear wasn't aligned properly and had started chewing it up. Crazy.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!