Hi Alan
My 2009 $/$ has a ford MT75 box, was always very stiff when cold, changed the oil to Amsoil and a shot off
http://activ8lubricants.com. no more probs.
Have used the snake oil additive for years in my Desert bikes and the Challenge Jeep with the AMC 360 lump, diffs and also mix it with grease for my Uj's and the Morgan front suspension.
I think there was a change in oil spec (lighter) from Ford to over come this problem as well if you have the same box?
Cain