What is 4a on a truck?

4a on a truck could refer to a few different things, depending on the context.

One possibility is that it could be the model or type of the truck. For example, a truck model could be designated as "Truck 4a" or "Model 4a". This would indicate a specific model or type of truck within a manufacturer's lineup.

Alternatively, 4a could refer to a specific feature or specification of the truck. For example, it could be indicating the size or capacity of the truck, such as a 4-ton truck or a truck with a 4-wheel drive system.

Without more specific information, it is difficult to provide a more precise answer.