Drive Axle Inspection on a Semi Truck – Its Not as Hard as it Sounds

Drive Axle Inspection

The term "Drive Axle Inspection" may sound a little intimidating to the average person, especially if you aren't accustomed to dealing with axles on a semi truck. Whether you’re a new big rig driver or just want to touch up on your knowledge, it’s crucial that you know how to do an inspection because it is a Federal requirement to inspect the vehicle prior to your trip each day. Most times, this process takes about 15 minutes.

The Inspection

It should be noted that while the axle housings themselves require little maintenance other than visual inspection for cracked or broken welds or loose mounting hardware, the seals and axle lubricant need a little attention periodically. Parts to check include:

  • Lubricant level to ensure it is filled to the appropriate level
  • Carrier-to-housing connection
  • Wheel seals
  • The pinion input or output shields to check for oil build up or dirt
  • The housing breather to see if it’s missing or damaged

Inspecting the Breather

A thorough inspection of the housing breather is needed to make sure that no contaminants are being let into the axle. If the breather is damaged at all it puts the lubricant at risk by allowing contaminants in. If nothing is damaged, confirm next that the breather isn’t clogged. If clogged, heat in the axle increases pressure inside the housing which pushes lubricant out through the wheel. This could result in a wrongful diagnosis of seal failure.

A small amount of vapor is released by the breather from the axle, causing the area to look dirty or wet. This light amount of wetness is normal and shouldn’t cause you any panic. If the moisture becomes excessive then just apply thread sealant to stop the leakage.

Checking Your Alignment

Checking your axle alignment is a vital part of drive axle inspection. Misaligned axles can result in big problems with steer tires, and even a misdiagnosis of your axles.

Measuring the frame and the drive axles in comparison to each other is another way of inspecting your drive axle alignment. To do this, make sure that the wheels are wedged in choks and your brakes are released. Next, measure the space between the axles and confirm that the it is similar on both sides. Don’t forget to measure the separation from the brake spider to the frame rail and make sure they’re similar as well. If you notice that they are not similar, you could be in need of a full-chassis alignment on your drive axles. It’s a service we are more than happy to offer you here at our shop.