talk with drivers about power takeoff (PTO) cables on tow trucks, the
driver often finds it baffling that the PTO cable is hard to operate on
one tow truck, and easy on another truck. One cable will be so
difficult to use that he needs two hands to push it in, while another
cable moves so freely it can be operated with one finger. Because I
also push and pull on PTO cables all day long, I'm sympathetic.
Factors Affecting PTO Cable
Three factors make the PTO cable
hard to push and pull: tight bends, overall cable length, and age.
Tight bends in the cable make the cable difficult to push and pull.
Route the cable so that all bends will be wide, not acute. Make
bends in an 8-inch radius or greater.
The longer the cable, the harder it will be to push and pull.
Lengths over 8 feet make operating the cable extremely difficult, even
when all other conditions are ideal. Cut the cable as short as it
can be without being so short as to necessitate tight bends.
The older the cable gets, the more corrosion it develops inside the cable
liner and the stiffer it becomes to push and pull. Although
lubricating the cable may help temporarily, solve the problem by
installing a new cable.
Point About Cable
The key point to remember is
these three factors add onto each other to produce the total effective
stiffness of the cable. If you have a long cable, it's going to be
hard to operate even if it's totally straight, and very hard if it has any
It's a good idea,
when the truck's in the spec'ing stage, to try and spec a combination of
transmission and cab which places the PTO shift cover in such a spatial
relationship with the desired location of the PTO knob in the cab that the
path of the cable between the two will be short, straight, and clear of