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If it Moves, Lube it!
One of the most overlooked maintenance requirements of the modern over-the-road vehicle is lubrication. This is of great concern because it is critical that each component is lubed at the right time with the right lube. The modern tractor has an engine that easily allows for extended oil drain intervals due to improvements in engine components, electronics, oils and the additives therein, but we must not assume that the rest of the vehicle can tolerate the same extension. I want to focus on lubrication points that typically do not gain the attention they deserve.
Let’s start with drivelines, due to the cost and downtime that typically occur when a vehicle experiences a failure in this area. Whether you do your own maintenance or take your vehicle to a qualified technician, the first step is the same. A thorough inspection must occur before lubricating a driveline. (It is impossible to properly inspect driveline components after lubrication because excess movement will be hidden by the applied grease.) In addition, each grease fitting must be cleaned to ensure that dirt and grit is not forced into the component, since that will reduce yield or lessen the life of the part.
U-joints are properly lubricated when new grease can be seen from all four bearing cap seals of each U-joint. On some yokes, if grease can only be seen from one cap seal, the torque should be checked on the capscrews of that seal. If the torque is OK and all of the seals do not purge, the caps must be removed in order to inspect the seals for damage. Damaged seals require a replacement of the U-joint.
The technician will observe the old grease coming out of the U-joint. Rusty, gritty, or burned grease requires a replacement of the U-joint.
The driveline components must be lubricated per the manufacturer’s recommendations or expensive repairs will be coming your way. Do not compromise here to save a few bucks. The cost of replacing a non-purging U-joint pales in comparison to replacing air tanks, air lines, brake chambers and possibly a transmission or rear-end due to a failed U-joint while the vehicle is in operation.
Lubricating the slip yoke is vital, but can be tricky. Grease should appear at the relief hole. Cover the relief hole with your finger until new grease appears from the slip joint seal.
Clutch Release Bearing
Many of the clutch release bearing failures we see today are due to an improper lubrication interval or poor lubrication practices. According to Eaton, their Solo clutch release bearing must be lubricated every 25,000 miles or once a month for on-highway vehicles.
Unapproved lubricants and improper lube procedures will cause premature clutch release bearing, bushing sleeve, and cross-shaft bushing failure. Many vehicles have a lube tube for the release bearing. The inspection cover should be removed to ensure that the lube tube is attached and not leaking. There should be enough lube applied to ensure the grease purges out of the release bearing housing onto the transmission input shaft. You want enough lube for the release bearing to move along the input shaft freely, but not contaminate the friction material on the vehicle’s clutch. Apply extra lube onto the transmission shaft between the release bearing housing and the clutch brake. Don’t worry about grease getting onto the clutch brake, as it will not affect its operation. Be certain to apply lube to the release yoke fingers to reduce wear to the pads. Finally, lube the cross shaft grease fittings and apply a good spray lithium lubricant to all moving clutch linkage components, such as ball sockets, yokes and yoke pins.
In general, the vehicle operator needs to be aware of the OEM-recommended intervals for lubrication, typically every 25,000 miles, thought that can vary. Drivers who operate mainly on city streets with a lot of stop and go may need more frequent maintenance intervals. Working long-term in a rainy environment can also affect maintenance intervals, since the rain will wash lubrication away.
Homer Hogg, Senior Technical Trainer for TA and Petro, has worked as a truck technician for 30 years. He is a Daimler Certified Trainer, Ryder Master Technician and a member of the Nashville Auto Diesel College Hall of Fame.
Homer Hogg’s “Maintenance Matters” airs on the Dave Nemo Show (Road Dog Trucking, SiriusXM 106), 8 a.m. ET, the first Thursday of each month.