Transmission Feels Bindy In Reverse
 

I have an 01' 4.6L 4x4 Super Crew with 220K miles on it- yesterday I put it in reverse and it felt tight/bindy- almost like it was in 4-low or something. This happened a few more times intermittently during the day so I parked it and am trying to decide what the issue could be so I can determine who to take it to. On a side note 3 weeks ago my O/D light blinked a few times- had the transmission flushed/serviced with Mercron Trans Fluid and it hasn't repeated. Could this be a transmission problem, a rear diff issue? Could the drive shaft be moving a tad and making it bind in the differential (some type of linkage, band, or mount off? Any suggestions would be appreciated. The transmission shifts great through all the forward gears and reverse feels thick half the time for 1 day.

Does the engine rev up at all when you're in reverse?

It doesn't rev and doesn't do it all the time. I stopped driving it but did back it up yesterday- was fine. It is also fine through all the forward gears. Any suggestions are appreciated