Improper driveline maintenance can lead to vibrations, noise and catastrophic failures. Pumps and other vital components can quit working, and vehicles can stop dead in the middle of the road. Adding a couple of easy driveline checks to your regular preventive maintenance program can help detect and avoid these problems.

Most emergency vehicles have driveshafts to transmit the engine power and torque to the rear axles. Vehicles with tandem rear axles will have a second driveshaft between the tandem axles, and those with 4x4 or 6x6 drive will have one or more driveshafts running to the front axle. Finally, vehicles equipped with pumps, generators or other components driven by power-takeoffs on the engine or transmission may have driveshafts connecting those components.

Each of these driveshafts usually consists of one or more tubular shafts with universal joints, shaft supports and slip splines. These parts need to be checked and lubricated as defined by the driveshaft manufacturer, or at least annually. They should also be checked any time the driver reports an unidentified vibration, shudder, noise or improper operation of any driven component.

When performing these procedures, always consult the apparatus, chassis or driveline maintenance manual for specific instructions. Here are some of the general conditions that may have to be checked:

Damage. Look for missing or damaged fasteners, yokes, caps and support bearings. Inspect the driveshaft for impact damage and broken welds. Check the slip splines for galls. Replace any missing or damaged components.

Looseness. Grab each end of the driveshaft assembly and shake it horizontally and vertically. Do this before you lubricate the U-joints because fresh grease can mask these problems. Consult the manufacturer if there is motion in any direction, as this will usually require replacement of the U-joint.

Discoloration. Check the U-joints for any discoloration of the metal that would indicate excessive heat build-up. This is usually the result of insufficient lubrication. Again, consult the manufacturer for further action.

Lubrication. Once all the components have been checked, wipe the U-joint grease fittings clean and add the appropriate grease according to the manufacturer's recommendations. Continue until fresh grease purges from each of the bearing caps. If any cap does not purge grease, use a hammer to gently tap on the yoke lug holding the cap, not the cap itself, while applying pressure with the grease gun. In some cases, the caps may have to be loosened slightly and held in place with a clamp. If any cap still does not purge grease, consult the manufacturer as this usually indicates a plugged internal passage and can lead to bearing failure. Also lubricate any slip splines equipped with grease fittings.

Some driveline problems are the result of improper design, rather than improper maintenance. They include shaft and U-joint failures caused by undersized driveshafts, slip spline galling or failures caused by improper driveshaft length and vibrations, or noise caused by unbalanced driveshafts or excessive U-joint working angles. These problems are commonly the result of modifications or additions to the driveline by the apparatus manufacturer. Some can be corrected, others can't. Consult the apparatus manufacturer for the appropriate action.