4wd range selector / vss in 747 application

["Niinikoski, Juha" <Juha.Niinikoski@mikrolog.fi>]

I don't have any 4wd truck wiring diagrams so can anybody help me on this. I
don't know if a switch is needed to inform 747 ecm if the transfer case is
in low range. If it is what is the input pin for this information ? Are
there other tricks how ecm handles lo range ? In my conversion easiest place
to build vss is inside speedo. This way it is always going to represent
absolute vehicle speed.

What I have understood so far is that vss input is important for ecm to
handle idle adjustments and prevent stall on decelerating conditions. What
is not clear for me how ecm handles same situations in lo range. Going
downhill you may have very low speed but same engine conditions than in road
speeds.

Thanks Juha
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