payload. The Federal Motor Vehicle Safety Regulations (49 CFR 393.85) apply and tell how to do it. See your local-legal
office for copies of the United States Code of Federal Regulations (CFR).
b. The power train and spring applied brakes must be disengaged on the disabled vehicle whenever recovery is
performed by towing from the front end. Towing from the rear end on the dead front axle is the exception. Those vehicles
with aux boxes behind the main transmission, including the CCE-IHC 20 Ton Dump Truck and the CCE-P&H 25 Ton
Hydraulic Truck Crane, need only have the aux box shifted into neutral to disengage the power train. It is a good idea to
wrap a couple turns of rope around the aux box cab control lever and tie the ends of the rope to fixed items in the 'cab.
This secures the lever in neutral and precludes the remote possibility of towing vibration or shock from accidentally
shifting the aux box into gear. Those vehicles with transfer cases or without an aux box must have the axle U-joint(s)
disconnected and the loose drive shaft(s) secured to a frame member. A second method of disconnecting the drive train
is to remove the drive axle shafts, wrap them in a clean cloth, and stow them in the cab. Trailer axle hub caps must be
bolted onto the hub to prevent entrance of dirt. Sets of trailer caps or metal plate equivalents are carried in the wrecker's
tool boxes. On most disabled vehicles the rear spring brakes have been applied. These vehicles cannot be moved until
the spring brakes have either been released by fully charging the reservoirs or manually caging each spring chamber.
Slave charging of the disabled commercial vehicle reservoirs to release the parking brakes should be used only for
tractor-trailer recovery to move the vehicle onto the low bed semitrailer. For hoist and tow and tow bar recovery, either
the disabled vehicle must be hoisted from the rear or the spring brakes must be manually caged. There is a danger in
towing of a commercial vehicle with fully charged reservoirs. If the air system has any leaks and if the driver guiding the
disabled vehicle uses the service brakes, the emergency-parking system may go into an automatic and uncontrolled
brake application while being towed. On older vehicles (pre-121), the spring brakes will "dynamite" somewhere about 45
to 60 psi reservoir pressure. On newer vehicles the spring brake application will gradually (or suddenly) begin brake
application after the reservoir has dropped below 90 psi with increasing torque as the pressure goes lower. CAUTION:
Caging of the spring brakes is only for the occasional emergency situation and the spring brakes must be
uncaged before returning to service. Caged spring brakes make the emergency-parking brake system
Truck-tractor semitrailer disabled vehicle recovery.
Loading of the disabled vehicle on a truck-tractor low boy
semitrailer, as cited above, is the safest,