01 shifts last 2 gears at the same time??

[komatsuvarna]

01 f 250 4x4 diesel with 108k. It shifts fine with the overdrive off, but if the overdrive is on and you take off from a stop it wants to shift the last 2 gears at the same time. Dont seem to do it as bad if you let off the pedal a bit. Ive had 2 7.3 trucks that done the same thing. Ive got in a habit of just shifting the overdrive manually to prevent it from double shifting, but whats up with this?

[FordNutz]

At what speed? It sounds like OD and TC lockup close to the same time/speed. Very common.

[komatsuvarna]

hum..... probably about 40-50 mph I guess. Havent really paid much attention to that, but I will.