Wheel-end seals are fairly complicated components made up of multiple parts with close tolerances. They also are vital to the safe operation of heavy-duty vehicles. For these reasons and others they need to be inspected on a regular basis.
Inspection intervals will vary according to vehicle vocation, the size of the vehicle and the type of wheel-end system. According to Leslie Kern, senior product manager, SKF Vehicle Service Market, the wheel-end system provider will specify inspection intervals.
Proper wheel seal care begins with proper storage and handling. According to the Technology & Maintenance Council (TMC), wheel seals need to be kept away from electric motors, welding equipment and sources of ozone.
Keeping wheel-end seals clean and dry is very important so do not place them on a dirty surface and wash your hands before handling them.
A good way to ensure that the seals stay clean is to store them in their original packaging until you are ready to install them. TMC cautions you never to store wheel seals in open bins where they can be exposed to contaminants.
Be careful not to drop seals because they could become damaged even though the damage might not be apparent. Do not use a wheel-end seal that has been dropped.
Handling seals properly will ensure they are ready to be installed as replacements if you find a problem during a wheel-end inspection.
According to Jon Intagliata, product manager, Dana Commercial Vehicle Systems and Roadranger, “The inspection starts with the driver prior to the equipment going into service.”
He added, “This ensures detection of a problem prior to a truck shut-down condition or major failure. These inspections also can reduce overall maintenance costs associated with vehicle operation by detecting possible signs of failure before the failure becomes costly.”
The first part of the wheel-end system inspection should be a visual check for obvious signs of leakage. Check the hub for dirt or grime and look at the brake linings for signs of oil splash.
These conditions are an indication that the wheel seal is leaking. Do not be concerned by a small amount of oil seepage; this can be normal. However if the brake shoes or the wheel is soaked with oil, there is a problem.
Proper lubrication leads to optimal wheel-end performance, so always check lubricant levels during your inspection as well.
Intagliata pointed out six items that need to be checked during a wheel-end inspection.
- Look for signs of dampness or leakage around the hubcap flange and gasket area.
- For oil-filled wheel ends, check the oil lube level through the sight glass of the hubcap for proper lube levels.
- For greased wheel ends, if possible, check for wheel temperature variation that might indicate improper grease levels.
- Inspect brake linings for dampness or leakage indications from the seal.
- Inspect wheel-end components for damage.
- Inspect the wheel seal area for dampness or leakage.
Another way to determine if there is a problem with the wheel ends is to touch them. They should be the same temperature. If one wheel end is hotter than the other, there is a problem. Hot wheel ends are an indication that not enough lubricant is in the system or that the bearing is too tight.
According to Kern, “Wetness at the hubcap, drive axle gasket or seal indicates that the wheel end requires internal inspection.”
She added, “With the axle lifted, rotate the wheel, place your hand on the frame and feel for vibration while listening for noise.” Vibration or noise indicates that you need to do an internal system inspection.
According to Rod Hodge, product manager, The Timken Co., “When inspecting seals, look for cuts, nicks, contaminants and grease seepage around the seal lip and outside diameter.”
In order to perform an internal inspection, you must pull the hub from the spindle. “Once the hub is pulled, the seal must be replaced. Never re-install a seal,” Kern said.
Looking at the removed seal can provide you with clues as to why the failure occurred, she explained.
If the seal leaked you need to determine why. Was the bearing too tight thereby causing it to fail? Was the lubricant contaminated with metal debris?
“The answer will indicate what further service is needed beyond a simple seal replacement. If all you do is replace the seal without finding the root cause of the failure, the condition will continue and there will be a subsequent failure,” Kern said.
Hodge added, “When inspecting a used seal, it’s important to note the wear on the seal lip to determine if it indicates misalignment or abnormal wear.”
Following the manufacturer’s installation instructions also is important for ensuring component longevity.
“Different seals require different installation procedures and tools,” according to Kern. “Using the incorrect tool could mean the end of a seal’s life before it even begins.”
To ensure extended seal and bearing life, follow TMC’s Recommended Practice (RP) 618 for wheel bearing adjustment procedures unless the component manufacturer indicates otherwise.
Hodge offered this advice for ensuring long seal life. “First and foremost, clean the shaft of debris and contaminants, which include nicks and burrs. Next, use the proper tooling to install the seal and make sure it is perpendicular to the housing or bore.”
He also advised applying a small amount of lubricant to the lip prior to seal installation. “This reduces the sliding friction of the contact surfaces and also protects the seal lip during initial run-in or dry start-up.”
“Using a dial indicator, verify that end play is between .001″ and .005″,” Kern explained.
Intagliata had several suggestions for ensuring long seal life. He said to practice proper wheel bearing adjustment, maintain the end play requirements per OEM specifications and refer to TMC’s RP618 and RP622 for the proper procedures for doing so.
“Make sure to use the recommended wheel-end lubricants per the OEM, wheel manufactures or refer to TMC’s RP631A,” he said.
Common wheel-end seal problems include the following.
- Use of the wrong installation tool causes 30% of failures.
- Spindle impact accounts for 15% of failures.
- Improper bearing adjustment leads to 15% of failures.
- A crushed seal causes 10% of failures.
- A cocked seal is responsible for another 10% of failures.
- Cleanliness issues make up 5% of seal failures.
- Other causes make up the balance of reasons why wheel-end seals fail.
“The most common problems with installation have to do with seal lip damage resulting from improper installation tools or improper handling,” according to Hodge.
This is why it is important to make sure the shaft is clean and the seal is free of cuts and nicks. “In addition, if a seal is installed at an angle or is cocked, it will deform the contact surface of the lip and create a leak path,” Hodge explained.
“Most seal failures can be avoided by using proper installation procedures,” Kern explained. “Using incorrect or damaged installation tools is the most common reason for a failure.”
The lubricant, seal, bearing, hub or axle can become contaminated during installation or contamination can enter the wheel-end system through the seal itself, Intagliata said.
Heat also causes problems for wheel-end seals. Low lubricant levels and high braking applications or brake drag are the biggest heat-related seal problems.
“When a seal is damaged, it no longer is capable of retaining the lubricant,” Hodge said.
“It also allows an ingression of contaminants, which causes early bearing failure. The contaminants fatigue the metal, which causes metal deformation or flowing known as stress points or spalling.”
He added, “This failure can cause extensive damage to the wheel-end system and could be as extreme as a wheel-off situation.”
Kern suggested performing a final inspection of the hub to make sure the seal is not damaged or cocked.
“In addition, a smooth, even hub placement will protect the seal from damage or movement.”
Also remember that an overtightened bearing adjustment can result in preload and can be disastrous, according to Kern.
If you handle wheel-end seals properly and inspect them according to TMC or the manufacturer’s guidelines, you should be able to spot any problems before they become serious and the seals will enjoy long life.
For More Information
For more information on wheel-end seals, you may contact the following companies directly or use the FREE Reader Service Card in this issue. Other companies offering information on wheel seals and other wheel-end components can be found in the Truck Parts & Service Aftermarket Buyers’ Guide & Directory as well as in the Buyers’ Guide section of our internet web site at www.truckpartsandservice.com.
Dana Corp.
HVTSS
Toledo, OH
419-866-3900
www.dana.com
Federal-Mogul Corp.
National Seals
Southfield, MI
248-354-7700
www.federal-mogul.com
Roadranger Parts Marketing
Kalamazoo, MI
800-328-6687
www.roadranger.com
SKF Vehicle Service Market
Elgin, IL
800-882-0008
www.vsm.skf.com
Stemco
Longview, TX
800-527-8492
www.stemco.com
The Timken Co.
Canton, OH
330-438-3000
www.timken.com
Triseal Corp.
Hebron, IL
800-910-7325
www.triseal.com
