Re: [MV] GPW/MB 4WD how often?

Gordon.W.I. McMillan (
Sun, 7 Dec 1997 17:55:10 -0000

If you do not have lock-out hubs almost everything should turn in
normal operation, though it has to be worth engaging low range and 4WD
occasionally just to keep things like shift linkages free.

I can think of at least one special case - the humble DUKW. When on
road all the systems turn as with any other vehicle, but in the water
the marine drive is in operation, and from memory this is hung off the
gearbox. Since DUKWs normally operate in 2nd or 3rd gear when in
marine drive (with the wheels out of gear) this means that the transfer
case input is turning all the time marine drive is running. GMC
transfer cases derive their splash lubrication from the gears in the
bottom half (i.e. the outputs) of the transfer case turning, as the
designers did not anticipate a case where the transfer case input would
be turning for long periods of time but not the outputs. (still with
me ? ) Upshot of all this is that the transfer case input shaft is
very poorly lubricated when a DUKW is driven in marine drive with the
transfer case in neutral. I remember one owner (in Germany) who had
arranged separate force lubrication for the transfer shaft input shaft
'cause he used it a lot in the water. As a further aside it is
impossible to use a DUKW starting handle to inch the vehicle backward
as it operates on the marine drive as well. Engaging reverse in the
main gearbox while turning the starting handle merely turns the engine
backwards - even your average DUKW owner isn't usually aware of that.
(with apologies for rambling on ) Gordon Falkirk, Scotland. 8-)

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