U.S. Federal regulations require that all manufacturers create a VIN number and attach it to a part of the vehicle that is durable, tamper-proof, and easily accessible without taking apart the vehicle. Because of the varying configurations of each type of vehicle (commercial boxes vs. sedans), U.S. Federal Regulations cannot establish uniformity in VIN placement among all vehicles. Therefore, while many passenger vehicles share a similar pattern of VIN placement, commercial box trucks, motorcycles, and other non-conventional vehicles will exhibit significant differences.
The vast majority of cars, SUVs, and mini-vans manufactured in the United States since the early 1980s include the VIN number on the dashboard, driver's side. The visibility of the VIN number from the exterior of the vehicle allows anyone (purchaser, inspector, law enforcement personnel performing a license plate run) to access the VIN number of the vehicle simply by approaching the vehicle from outside and viewing the number through the windshield. Generally located at the upper edge of the windshield meeting the top of the dash, the VIN number is stamped onto a thin piece of metal or plastic that houses the complete seventeen character string.
In addition to being located on the dashboard, nearly all new vehicles contain a backup VIN sticker on the driver's side door jambs. While primarily containing the VIN number, most door jamb stickers also list several other pieces of important information such as tire inflation specifications, manufacturing date, color codes, and trim level data. These stickers serve two distinct purposes; they provide a second source for verifying the VIN number if damage occurs to the dashboard plate or if the dashboard plate is removed and/or replaced. They also make it much more difficult for someone attempting to deceive others regarding the authenticity of a used vehicle by substituting or altering a false VIN sticker(s).
Most standard pickup trucks will follow the same dashboard plus door jambs model as passenger vehicles. However, as we transition into larger trucks, commercial vehicles, or any vehicle utilizing a frame/chassis configuration separate from the body of the vehicle, we begin to see reliance on frame rails.
The most notable examples of this would be large trucks that were originally designed as a bare cab/chassis prior to having a specialty bed/box/equipment mounting platform installed by another manufacturer. As a result, VIN number plate location location can vary depending on how and where final assembly took place and not strictly based on design intent by the original chassis manufacturer.
As mentioned previously, most passenger car owners have no knowledge of this area due to it being specific to large trucks, commercial vehicles, trailers and some heavy duty applications. Typically located on the driver's side underframe rail (the longitudinal structural steel member) nearest the front axle, a vinyl coated aluminum or stainless steel sheet stamped with the vin # is affixed to this rail.
The rationale behind frame rail stamping stems from commercial/heavy duty vehicles undergoing construction in multiple stages. The chassis manufacturer produces/stamps a vin # on the frame rail during production and then provides it to a separate manufacturer who installs the body. Even though the remainder of the vehicle receives modifications after it leaves the chassis manufacturer's facility, the vin # on the frame remains constant throughout this multi stage build process.
If you are purchasing a commercial/heavy duty application and inspecting said vehicle, and you notice inconsistencies between what appears to be the vin# on the cab versus what actually is present on the vehicle's age/use history, checking for vin # presence on the frame rails is advisable.
Unlike automobiles which utilize a combination of plates and stickers for vin # identification, motorcycles have vin #'s stamped directly into the steering head. Since motorcycles endure much harsher environmental conditions than enclosed automotive cabins, vin #'s on motorcycles are typically stamped directly into the metal.
While some motorcycles may display secondary vin # stickers in various other locations along their frames, the steering head stamped vin # is generally considered to be authoritative for both registration and insurance claim purposes as well as recall notifications.
Many engines carry their own vin # stamped directly onto them; however, this is typically not an identical vin # as found in other areas of the vehicle. Rather than providing an exact duplicate vin #, these shorted engine seriel numers identify an individual engine. This difference becomes relevant when determining whether an engine was swapped/replaced in a vehicle or otherwise modified.
When purchasing a used vehicle where discrepancies exist between expected vin #'s based on either vehicle information plate data or engine serial numbers, this fact should be noted particularly in situations involving insurance claims/emissions testing/pre-purchase inspections.
There are occasional instances where additional vin # related information may appear in areas such as:
Underneath the spare tire well (most likely in hatches/sedans)
Stamped into firewalls/engine bays on some models/manufacturers
Inside glove compartments (some makes/models/year)
Titles/registeration/insurance documents that match physical vin # exactly