Shop Talk: DOT Inspections – What Every Owner Needs to Know

Categories: Shop Talk

Felix Elizondo US Transmission


Felix Elizondo’s knack for mechanical solutions over the decades has crystalized into impeccable On-Highway and Off-Highway diagnostics strategies since 2010. Felix is certified on Allison, Kubota, and Benchmade brands and has been part of the Catalyst Powertrain service team since 2016.


This is a Q&A session where we discuss the surprising results from DOT inspections and help owners understand ways they can save on repair costs.


Why are DOT Inspections Important?

First, they’re required by law to be done every year to ensure we have safe vehicles on our roadways. Second, it’s the most common way equipment owners learn about mechanical issues they may not otherwise know about.

For instance, if a truck is overdue for a maintenance check, chances are something is getting worn down or worn out. A vehicle is really an interconnected system, so if something wears out, or a small part breaks, the risk immediately increases that it’s going to affect something else. DOT inspections don’t replace regular maintenance, but you’d be surprised at what is uncovered.

What are the Most Common Maintenance Items Discovered During a DOT Inspection?

Brakes, tires, seal leaks, and lights tend to be the most common issue we see. Catalyst Powertrain performs the full DOT Inspection, but we go a bit deeper, too. We’re adamant about making sure vehicles are safe to operate because the human cost is too great. So, while the DOT Inspection list is comprehensive, we go a little further. For instance, we examine every single grease point. This isn’t a DOT requirement, but we do it because it’s important, particularly in the Pacific Northwest. With wet road conditions, the grease tends to wash away. Now you have points on the vehicle that are no longer protected. Water is relentless. Once rust or corrosion takes hold, a small problem can quietly incubate creating a much larger problem that isn’t necessarily visible until it becomes a critical failure.


Fluid leaks addressed with regular maintenance save thousands in needless repairs.

Why are Tires a Common Problem?

Because vehicles are a series of connected systems, tires can wear out because of suspension issues. If the suspension is worn out, the tires wear out much faster. At thousands of dollars, tires aren’t cheap. Owners can save themselves a bundle by replacing less expensive replacement parts on the suspension. The alternative can result in blowouts on the road. Getting stuck, possibly hurting someone, even the cost of towing makes doing simple suspension inspection checkups worth every penny.

What About Suspension?

If tires are wearing funny, owners should bring the vehicle into the shop. When the suspension is worn out you’ll get uneven wear patterns on each tire of the truck. The front driver’s side, for example, might be worn out on the inside but the passenger side tire is worn out on the outside.  This indicates a suspension problem. Clunking sounds, lots of play on the steering — kingpins are notorious for failing on trucks. Kingpins need regular greasing, especially in the Pacific Northwest. All that rain, water is washing away the protective grease that was coating the components. This washing away wears out components faster with corrosion and rust.

What About U-Joints on Drivelines?

U-Joints on drivelines are another system impacted by a lack of grease fittings. About 90% of customers have dry U-Joints. If they’re dry and worn out, and the driver is traveling 65MPH on the freeway, a driveline that is spinning dry without grease will heat up and possibly break the U-Joint. Without proper lubrication, vibration will travel up to the transmission and break things on the inside of the transmission.


An HD4500 with catastrophic failure due to driveline issues.

How Often Should I Bring My Truck to Catalyst Powertrain for Maintenance?

It’s a good idea to do a thorough inspection at least once a month to prevent those bigger problems and nip smaller ones in the bud. If trucks are used in the City, they get more wear compared to trucks on the highway. The amount of stop and go, plus the weight of the truck — and its cargo — creates more wear. There is more consistency on the highway so the engine runs at a relatively constant speed longer. Less change means fewer chances for problems. It’s always up to the owners and drivers to determine if the vehicle should come in for maintenance before the recommended guidelines.

For owners and drivers, we recommend reviewing a checklist of the basics that will help inform them if the vehicle in question should come into our service center sooner than the scheduled maintenance date.

How Long Does it Take for a Catalyst Powertrain DOT Inspection?

Usually, it takes about an hour. The most common truck we see is the Freightliner. Those often go quick, because everything we need to inspect is right under the hood so to speak. Visual checks are easier. Other makes are designed differently and some areas we need to inspect take longer because of how the truck is designed.

If we find things that need to be addressed, we’ll call the customer and inform them of the truck’s status and we’ll provide recommendations to get the issue resolved. If it’s something simple, and we have the part in stock, we can usually work that right in during the inspection time.

Aren’t Brake Issues Addressed During Regular Maintenance?

They are, but the issue is bigger than just routine maintenance. It all depends on how a truck is driven, what happens to the vehicle on a daily basis, and in what environment, at what temperature, and in what weather conditions it is operated. Most owners have their vehicles inspected once or twice a year as part of regular maintenance.

But they may not know the particulars of the driver’s roadway habits. If the vehicle is run rough, the window for maintenance shortens. This is something we can see evidence of in our DOT inspections and regular maintenance services.

If a driver doesn’t notice an oil leak, for instance, that oil can leak into other parts like the brakes. Once oil touches the brake pads, those can’t be reused. If enough time and wear go by in this condition without an inspection, there’s no going back, and the risk goes up dramatically. The cost suddenly jumps from around $600 or so up to $2,400 and up for replacements, towing, and other expenses. That’s why it’s always important to keep tabs on the vehicle in case something is a little out of the ordinary. It can save owners thousands of dollars. Axel seal leaks are very common on diesel trucks, so again, if we catch those at the right time, we can save the brakes.

If My Truck is Leaking Fluids What Should I Do?

If you are losing a quart every minute, drive it to the shop. We can get that truck serviced quickly. If it’s a filter problem, we can take care of that right away. If it’s something else, like the rear main seal, then we need more time because we need to remove the transmission in order to get to the rear main seal. The important thing is not to wait — when one problem presents itself, the risk is high it is impacting something else. Many issues we see are a result of this domino effect.

One of the advantages we offer is that we have wheel lifts – most of the other shops out there don’t have these. This saves hours and enables us to get trucks in right away. The technician doesn’t have to be on their back in a tight or awkward position. It’s easier to get to what needs to be inspected or repaired.

Coolant leaking into a transmission.


What About My Allison Transmission?

We love Allison. They make great products and we know owners understand this. The fact that these are the true workhorse in the industry means sometimes owners are tempted to skip the regular maintenance these transmissions require.

For example, if maintenance isn’t done every 75,000 miles or 3 years, it’s because the thinking is Allison is a good brand. But the truth is, it is still a machine and needs regular maintenance. By keeping up with routine maintenance, owners will pay somewhere in the neighborhood of $400 on a service inspection. This is much more affordable than the average $6,000 or $7,000 (or more) repair that would be needed if something goes wrong.

The weather, vibrations, and other factors start to add up over time. That’s what regular maintenance can do to give the transmission or any other part on the vehicle a longer lifespan. Tightening something up, or replacing a smaller part, is faster and less expensive than waiting until something else is affected and starts breaking down the whole system.