I understand about not having live axel 4WD because of the turning problems that go along with it. I just wasn't sure if the 455D has some type of posi-traction unit (GM term) where both wheels would drive and then a limited slip clutch unit would allow for the two different axel speeds in a turn.
I think the area to look at is the high speed switch the same as the seat switch gave me my prior problem. Although I only used high range on one occassion, several times a season for 5 years I would move the range lever into neutral so I could pull the unit out of soft ground and this going in and out of range might be the reason for my sporadic 4WD, due to a malfunctioning switch. I will check out the wiring diagram for the circuit and report back. Thanks