What Do You Mean I Need to Fill the Hubs?

Meritor Wheel Ends Truck Repair Information and Tips

Some mechanics are so familiar with wheel ends that they probably can’t even remember the last time that service information got a glance, with the exception of a specification every so often. On the other hand, there are also those who rarely get the opportunity to service wheel ends.

Regardless of which group you may be in, almost every mechanic can say they have at least had the hubs off of the rear axle of a pickup at some point in their life. You may remember smearing some grease around those rear-wheel bearings of that old pickup, filling the differential back up, checking the hub oil level and calling it good.

With heavy trucks, your experience is going to be a little different. For instance, a lot of weight is going to rest on those wheel end bearings, and they’ll need lubrication. So how does that happen or not happen as the case may be?

Let’s take a look at Meritor drive axle ends as an example. Some Meritor hubs come equipped with a fill plug that ensures the proper amounts of lube oil are added. However, always be sure to check the service information for the specific vehicle being serviced. Here is the general procedure:

  1. With the axle level, rotate the hub fill plug to the top and add two pints of the specified lube oil.
  2. Reinstall the plug, and tighten it to specification. Make sure the axle is also filled with the proper lube oil.
  3. Road test the vehicle at slow turns, making several full turns in both directions.
  4. After returning to the shop, let it sit for 10 minutes.
  5. Check for any leaks, and recheck the axle fluid level.
  6. Top off the differential as needed.

Now, what do you do when there is no wheel hub fill plug? Well, the process gets a little more interesting.

  1. First, make sure the vehicle is unloaded.
  2. When assembling the wheel hub, the bearings should be dipped in the same lube oil as specified for the differential.
  3. Before the axle shafts are reinstalled, make sure there is additional oil brought out to the wheel ends. To accomplish that, check to see the differential is filled to its proper level.
  4. Then, raise one side of the vehicle approximately 12 inches, and wait for the oil to start coming out of the hub.
  5. Once it does, lower the vehicle, and repeat to the other side.
  6. At this point, complete reassembling the axles and hub.
  7. Top off the differential lube oil as specified in the service information, and test drive at slow speeds, making several full turns in both directions.
  8. Return to shop, and check for leaks. Allow the vehicle to sit for about ten minutes to allow lube oil to settle, and recheck the level.
  9. Add lube oil as needed.

While heavy-duty wheel ends are quite different than those of an old pickup, much still remains the same. For the mechanic, the important part is to ensure the job gets done right to keep those out on the road safe as well as avoid shop comebacks. You can refer to the repair information in TruckSeries from Mitchell 1 for detailed specifications and procedures for servicing wheel ends.

About the Author

Jake Schell

Jake Schell is an editorial consultant with Mitchell 1. Previously, he served as Product Manager for the Commercial Vehicle Group from 2002 to 2023. Prior to joining Mitchell 1, Jake spent 20 years as a technician. He holds a Chevrolet Master certification in the transmission category as well as ASE certifications in both cars and trucks.