A four-wheel drive assist for electric machines includes an electric drive system
for driving wheels at a non-steering end and a selectively operable hydraulic system
for driving wheels at a steering end. A controller controls the operation of the
drive system according to operator selection and/or by detecting slipping of the
electric drive system. Preferably, at least one hydraulically driven operating
arm, including boom functions, lift platform, etc., is driven by the same hydraulic
pump that drives the steering end hydraulic system. The machine thus is capable
of effecting four-wheel drive when necessary, while operating as efficiently as
a conventional two-wheel drive full electric machine when the four-wheel drive
system is not engaged.
