How to Locate Identification Numbers on Heavy-Duty Truck Parts

When customers call in to look for a part from the TPI inventory, we will often ask them for part numbers or other identifiers in order to make the search more accurate and efficient.  Other than a VIN number however (which is also included in registration papers), it is not always easy to find where these numbers might be found on the parts.  In this article, we will talk a bit about general locations and the types of numbers to look for.

General Information

In general, finding identifying numbers on a part is not an obvious task.  Each manufacturer will have their own place to put numbers, and this place will sometimes change between models.


As mentioned above, a VIN number can be found on registration or title papers for the truck.  If you don’t have these on hand, you will be able to find the number in one of several places, depending on the make of the truck. For example, a Peterbilt will often have the number under the lock on the side of the driver’s side door, or on a plaque underneath the steering wheel.  Alternatively, some trucks will place the VIN on the frame itself, not always the easiest place to get to.

Above:  VIN found on the door frame of a Peterbilt.

Above:  VIN found next to the steering wheel in a Peterbilt.


In addition to knowing the model of the engine you are looking for, it is always useful to have the serial number and CPL (Control Parts List) or ARR number on hand. Both of these identifiers can be found on a metal plaque called the engine data plate that is on the engine but, again, it is in a different place for each manufacturer and model.  In general, however, it should not be that difficult to find.

Engine data plate on a Cummins.


If you have the VIN number, you will be able to find information on your transmission.  If not, then you can look for a code that is stamped onto the case or a tag that has been riveted to it.  If you can find neither one of these, then you can take a look at certain features which will help determine what kind of transmission you have. For example, what shape is it (square, like Louisiana or Texas, etc.)?  How many bolts are there? All of this information will help the parts dealer in the absence of any other identifying information.

If your transmission has a plate, it will be found on an area such as this one (there was a plate here at one point, but somewhere in its travels it fell off).


Again, different manufacturers will put the identifying numbers in different places. With Rockwell, for example, the numbers can be found on the front of the axle shaft cover and on the edge of it.  Take a look around the part to see if there is either a tag or embossed numbers.

A Rockwell axle cover with numbers on the front…

…and on top.

Locating parts when you really need them is not always the easiest of tasks, but TPI makes it more efficient.  And, the more information you can have when you call in, the faster we will be able to help you find your part.