There are two configurations for a tandem truck... the first - more common in Europe - is known as "single screw". The driveshaft goes to the differential of one axle, and that's the only live axle. In cases such as this, the additional axle is typically a lift axle.
In N. America, tandem trucks normally use a twin screw configuration, where the driveshaft goes to a power divider... that power divider is essentially a differential, and has outputs going to both axles... ergo, both axles have power supplied to them at all times. A lot of people think that the power divider lock engages one of the axles.. this is not true.. it simply locks the outputs so that they always rotate at a matching speed.
Both of them.
You need to be more specific about the configuration. Is a single axle straight truck, a tandem axle straight truck, a tandem axle straight truck with additional lift axles, a tractor trailer...?
A tandem truck usually refers to the amount of axles on the trailer or tractor. A single drive axle on a tractor would be referred to as a single, or the same for one axle on the trailer. I have seen it referred to the amount of tires on the end of an axle. When there are two tires on the end of the axle, that would be referred to as a dual, not a tandem.
The "tandem" part means it has two drive axles, although it is possible for a tandem truck to be a 6x2 vehicle, and have only one of those be a live axle.
The exact same thing as the first drive axle.
A standard tandem load typically holds around 10 cubic yards of material. It can vary slightly depending on the specific dimensions of the truck bed and how the material is loaded.
In a single axle, most likely so. In a tandem axle, probably not.
40,680 lbs.
There's no such thing as a one axle truck. There has to be a minimum of two axles. "Single axle" if a term referring to a truck with only a single drive axle, and doesn't count the steer axle. Same with "tandem axle", "tri axle", "quad axle", and "quint axle".
They come in many sizes and configurations. They could be single axle trucks, tandem axle trucks, tandem axle truck with additional lift axles, tandem axle trucks with a twin steer setup (and these may also have additional lift axles, as well), and even tractor-trailers with mixer trailers. You'd have to be a little more specific as to which one you had in mind.
Well, the question is really too vague to be answered. You said gross weight, implying you want a loaded weight. Volvo manufactures and sells many different models of trucks worldwide. We have no way of knowing if you're referring to a Volvo truck in the United States, South Africa, Australia, the United Kingdom, etc. The allowable gross weights will vary between jurisdictions. Also, you did not say what configuration of truck - again, for all we know, you could be referring to a single axle straight/rigid truck, a tandem axle, a tandem axle with additional lift axles, tandem axle twin steer, single axle articulated truck, tandem axle articulated truck, etc. Typically, however, a sleeper cab truck and daycab truck are allowed the same gross weights.
Tandem axle dump truck. In some states, you may be able to put up to 15 tons on a single axle with an additional lifting tag axle.