In my
last column I wrote about how to troubleshoot PTO cables that are hard to
push and pull. In this column, I'll cover applications that require
a PTO activation device other than a PTO cable.
Cabover chassis, import chassis,
and automatic transmissions commonly don't work well with PTO
cables. On cabover chassis and imports, the tilt cab requires such a
great length of cable to run all the way to the front cab pivot and back
up into the cab, the PTO cable ends up being very hard to push and pull.
Automatics have two qualities
which make a PTO cable inadvisable: the PTO shift cover is often in
an inaccessible spot, and the need to stop the transmission gears by
putting the automatic in drive or reverse in order to engage the PTO
proves difficult for some trainees to understand, leading the trainee to
yank the PTO cable into gear when the transmission is in park or neutral,
thereby grinding down the PTO gears and sometimes jamming the entire
transmission to a stop.
Avoid these problems by
installing a non-cable-operated PTO shift cover on cabovers, imports and
automatics. An air-shift PTO, for instance, eliminates the cable by
using chassis air to engage and disengage the PTO. On chassis that
do not have air, install an electrically-activated PTO cover, such as the
E-Hydra Shift from Muncie Power Products. The photo shows an E-Hydra
Shift PTO I installed on a Jatco automatic transmission in an Isuzu NPR
cabover chassis.
Muncie's E-Hydra Shift is a
sealed unit in which an electric motor turns a hydraulic gear pump.
The hydraulic pump operates a cylinder, which engages and disengages the
PTO. This model of PTO cover has two features that make it well
suited to tow truck applications: the cylinder which contains the
electric motor and hydraulics can be rotated to point in any direction to
provide clearance with other hardware, and the E-Hydra Shift has a small
protuberance that can be used to manually disengage and engage the PTO in
a no-power situation.
