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Troubleshooting Article Archive:  March 2007      
Non-Cable- Operated PTO Activation
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.