Lack of lubrication can cause the U-joints to fail and cause extensive damage to the transmission. The U-joints are located in a couple of different locations on the motorhome chassis and you should pinpoint each U-joint position to assure that all of them receive regular lubrication. U-joints are lubricated at the time of manufacture, and should thereafter be lubed every three months or 10,000 miles.

Follow a few important safety rules while working on the U-joints. Park the motorhome on a flat and level surface and chock all wheels. Turn off the engine before going under the vehicle. For added security, remove the keys from the ignition. Chassis lubricant should be a high quality, non-corrosive multi-purpose lithium soap base that is water resistant and designed to withstand extremely high operating temperatures.

One of the most important lubrication points is the drive shaft. One end of the driveline is attached to the rear of the transmission, and the other end is attached to the drive axle. The power from the engine and shifting from the transmission will work together with the driveline and U-joints to provide power for the rear drive train.

Perform a comprehensive inspection of the U-joints and the driveline assembly under the motorhome. Look for rust at the splines and U-joint caps. Check the drive shaft for loose bolts. Make sure the drive shaft is clean and free of debris. Any U-joint or cap that appears damaged should be immediately replaced. U-joints and caps with excessive grease build up should be wiped clean to allow for a good visual inspection.

Clean grease fittings prior to lubrication. Make sure the equipment used is capable of pushing grease through the driveline assembly. When greasing the driveline it is important that new grease exits from each bearing cap. The U-joint trunnion is shaped in a cross with four bearing caps positioned at each U-joint. When you see grease coming out of all the bearing caps, the U-joint is then full of grease. Some U-joints also have two grease zerks on one trunnion. If the U-joint on your motorhome has two grease zerks it is required that you grease both, not just one. When greasing the driveline, continue adding lubricant until new grease is seen at all the caps. This will enable the new grease to remove contaminants that can cause wear and tear on the driveline system, drive shaft vibration or drive shaft failure.

It is important to grease the driveline spline. Lacking grease, the splines can become worn and stiff, restrict the driveline from moving in and out, and result in failure of the transmission seal.

Unless you have specifically requested that the U-joints and driveline be lubricated, don't assume that a service technician has performed the work. Ask for a list of specific points that were lubricated, and take a moment to visually inspect under the vehicle to be certain nothing has been overlooked.