vanguard2010

Recently had my 150 start locking up while backing up. Almost sounds like the breaks are applied hard and fast. I can then go forward and back up again. Sometimes if will lock up and sometimes it won't. Not sure whether I have a transmission, rear end, or brake problem. Any guidance would be appreciated. The engine is the 5.4 and the truck has about 90k miles. It has been well maintained up to this point.