I have a 2005 3500 dodge not sure exactly what the problem is but when I'm driving I have no issues with the tranny until I'm going over 110 km/hr and going over 2000 rpm
when I do go over that speed it's like my tranny slips it's down shifting on me andirs like it can't figure out what gear to be in
thinking it's the the over drive but not 100%
any help would be greatly appreciated hoping I don't need a Tranny rebuild
thanks

 

My 99 od went nuts. It was the output speed sensor. About $35 bucks. You can change it yourself. Worth looking into.