They both are.
They both are. The driveshaft goes to a differential (the power divider), which supplies power equally to both axles.
The exact same thing as the first drive axle.
They both do. The driveshaft turns a differential which distributes power to both axles.
In a tandem drive axle system, power from the engine and transmission is fed to BOTH axles equally. In some cases, such as military and very heavy construction vehicles, power is delivered to a transfer case located between the axles and delivered to them via drive shafts. In over-the-road trucks, such as semi-tractors, the power is first delivered to the front differential. Bolted to the front diff is a power splitting device, such as an inter-axle differential and, if it is a two speed system, a gear reduction unit. The interaxle differential is used to allow the front and rear axles to travel at different speeds when cornering. As the power comes out of the inter axle diff/speed reduction unit, it is split into two pathways. The first, connects to the input pinion of the front differential and drives the ring gear. the second pathway is an output shaft which passes through the rear housing cover on the front diff and connects to the rear diff input pinion with a short drive shaft.
If your vehicle has 4 wheel drive, then yes, it has a differential in the front axle.
A tri-axle has two live axles and a lift axle.. if it's located in front of the drive axles, it's known as a pusher... if it's located behind the drive axles, it's known as a tag axle. With a tandem axle setup (which is what tri-axles, quad axles, etc. are, albeit with the addition of dead axles), the driveshaft runs from the transmission output to the power divider. The power divider is a differential which transmits power evenly to both live axles.
Four wheel drive tends to be lighter, and less complex.. with a six wheel drive (such as in the M35, M39, M913, etc. series military trucks), you usually have to have an interaxle differential lock. In normal operations, tandem axle trucks, such as dump trucks, tractor trailers, etc. only have one axle which drives them forward. When they need to, the driver can engage the differential lock to engage the second drive axle. On a 6x6 truck, such as the type described above, the transfer case would be used to engage the front axle.
A trans axle is a transmission and differential rolled into one in a front wheel drive vehicle. The trans axle delivers power from the engine to the drive wheels.
I believe it's called a trans-axle output shaft seal. Could also be the front differential pinion seal.
There is no differential. The transmission is both a transmission and front wheel drive trans axle. It is all in one.
Front axle 12,000, Front tandem 34,000, Rear tandem 34,000 unless it is a spread axle trailer; then it is 40,000 for the two rear axles combined. Total weight not to exceed 80,000 lbs.