by Jim Kerr
Boating is a fun summer past time. You can see them being trailered to lakes and rivers all over our country. What you may not notice, is how the boats are unloaded from the trailers. Usually the trailers are backed down a sloping boat launch until the boat is floating in the water. Then the boat can be moved off to the dock while the trailer and tow vehicle are parked. This is the easy way to unload a boat, but it can cause problems with your trailer and your tow vehicle!
The problem is water gets into the wheel bearings on the trailer and the rear axle on the tow vehicle. Water causes the metal bearings to rust, and the rust causes the bearings to fail. When a bearing fails it can damage or break the axle shaft and could even cause a wheel to fall off!
Keeping the trailer wheel bearings out of the water can be difficult. Usually the wheels must be almost all the way under water before the boat will float off. The seals on the trailer axle are designed to keep out splashed water and dust, but have difficulty in stopping water when they are completely submerged. The key to long wheel bearing life is regular inspection (a minimum of once a year), repacking the wheel bearings with quality wheel bearing grease, and replacing the axle seals whenever the bearings are inspected.
When inspecting the wheel bearings, you should wash them completely clean with a solvent and let them air dry. Then inspect the rollers and the races (the surfaces the rollers ride on) for any marks. An even grey or frosted appearance indicates a good used bearing. Rusty spots, grooves, pits in the metal, and blue or black spots indicate problems and the bearings should be replaced. Blue or black colour indicates the bearing has been running hot. This can be caused by using the incorrect wheel bearing grease, the wrong amount of grease, improper bearing adjustment, or too heavy a load on the trailer.
When repacking the wheel bearings, each bearing (there are two per wheel) should be packed with an amount of grease the size of a golf ball. Too little grease allows metal to metal contact and produces wear. Too much grease can cause a heat build up in the bearings. and wastes grease. I see some bearing hubs that are filled completely with grease. This is not necessary. Place a little grease on the lip of the axle seal and a coating of grease around the edge of the dust cap on the end of the axle. This will help seal these areas.
Adjust the wheel bearings with the wheel supported safely in the air. Rotate the tire while slowly tightening the axle nut until just snug. Specifications typically are between 10 and 15 ft lbs. of torque if you own a torque wrench. Then back the nut off and tighten it just snug by hand. Finally, rotate the axle nut back off just until the first opening for a cotter pin lines up and install a new cotter pin. Replace the dust cap, lower the wheel, and you are ready for towing.
Here is one more tip to help keep water out of your trailer axle bearings. Unloading the boat immediately after driving on the highway will make more water enter the trailer axle. The wheel bearings produce a little heat as they rotate. This causes any air inside the wheel hub to expand. When the hub is backed into cold water the air inside it quickly cools and contracts. This pulls water in past the axle seals and then the water can start to rust the metal. Let your boat trailer sit for a while before unloading your boat. This lets the bearing hubs cool before they hit the water.
Sometimes the driver backs the tow vehicle too far into the water. This can let the water enter the rear axle of the tow vehicle. Many vehicles used to pull trailers are rear wheel drive, so this applies mainly to them. There are two ways the water can get in: past the seals, or through the axle vent. The vent is located on the top of the axle housing one one side of the differential. It is a small hole that lets air in and out of the axle housing as it heats and cools. If there was no vent, oil would be forced out the seals each time the axle housing heated up and the air inside expanded.
If your vehicle has been in water deep enough to go over the centre of your wheels, then water may have entered the rear axle through the vent and the oil should be changed. Changing the oil on most vehicles involves removing the rear cover, letting the oil drain, cleaning and installing the rear cover using a sealant, and filling the axle with gear oil. It is not a difficult job but can be messy and time consuming if you do not have the correct tools. Gear oil has a lasting odour and the smell can stay on your hands for several days even though you wash well. You may wish to leave this job to your service shop. Some vehicles have a drain plug for the rear axle. This makes servicing much easier.
Leaving water in a rear axle can cause all the bearings to rust and the differential to fail. The cost of overhauling a rear axle can easily run over a thousand dollars so a little preventative maintenance will help prevent big repair bills.
Finally, if you drive a four wheel drive vehicle the manufacturer has expected you will get into deep water or mud at some time with your vehicle. The axles, both front and rear, have vent hoses with one end attached to the differential and the open end mounted up higher on the body. If you get that deep in water you will have more problems than just water in the axles! Check these vent hoses when doing your regular oil changes as they can break or be pulled out of position during off road driving.