The heavy duty power steering applications in commercial, construction, and other large vehicles your shop might deal with have been specially developed to perform under pressure (quite literally). However, when it comes to rebuilding those applications, you need to know what parts you're working with and what makes them different from standard, lighter duty applications, and that's not always easy.
In this article, we'll describe how to identify heavy duty power steering pumps and gears as well as what to look for when purchasing heavy duty rebuild parts.
What vehicles classify as heavy duty?
To understand how to identify heavy duty power steering pumps and gears, we first need to explain how the vehicles they're installed in are classified. Whether or not a vehicle uses heavy duty power steering parts depends on its weight class. Vehicles are organized by numbered classes from 1-8, where Class 1 vehicles are the lightest and Class 8 vehicles are the heaviest. Typically, Classes 1-3 are considered "light duty," Classes 4-6 are "medium duty," and Classes 7-8 are "heavy duty." However, it's important to note that for some manufacturers, including TransTec, medium and heavy duty vehicles are considered as a compound category because the same rebuilders tend to rebuild both of those classifications.
So as a general rule, heavy duty pumps and heavy duty gears are for Class 4-8 vehicles. To give you a better picture of what types of trucks and vehicles are included in the heavy duty category, you can think of heavy duty applications ranging from use in commercial vehicles like a delivery straight truck used for transporting product from a local warehouse to distribution points all the way up to the full size semi trucks that transport product from one side of the country to the other as well as dump trucks and other construction equipment, too.
Here's a handy chart to help you identify a vehicle's weight class and whether or not it's considered "heavy duty" by the standards above.
How to Identify Heavy Duty Pumps and Gears
While heavy duty pumps and gears look similar and serve a similar purpose to their corresponding general light duty parts, heavy duty parts have several identifying features that set them apart. This diagram from SAE International shows the configuration of electrohydraulic power steering in heavy duty applications.
To identify heavy duty power steering pumps and gears, here are a few things to look for:
- First, heavy duty power steering components are much larger in size than light duty parts. This should be the most easily identifiable difference between pumps and gears for light and heavy classes.
- Heavy duty pumps are gear driven, as opposed to light duty parts, which are belt driven. Because the heavy duty pumps produce a lot more pressure than a typical pump, a belt drive would not be adequate on these parts. Heavy duty pumps are normally driven using a gear that is connected directly to the engine to prevent slippage.
How to Choose Quality Heavy Duty Pumps and gears
In any rebuild job, you always want to use parts you can trust. You simply cannot complete a quality repair without quality parts (read more about the importance of a quality rebuild in our recent post here). When it comes to heavy duty power steering, your quality concerns should revolve around the amount of high pressure the pumps and gears can withstand. Compared to lighter duty systems, heavy duty power steering systems need stronger parts that hold up. For instance, where a bushing might be enough to handle a standard application, a bearing would be used in a heavy duty setting. Not only do those heavy duty parts withstand more pressure, they also see increased daily run times and need parts that protect against excessive heat and premature wear and tear. A quality heavy duty application will also feature more robust seals that provide the same strength and protection. Overall, it's critical that you know the heavy duty parts you're installing have been tested and proven to withstand the pressure demands on today's heavy duty vehicles.