There does exist a 21 speed transmission, although I have yet to see one. 18 is the highest you'll normally encounter.
As many as the purchasing agent ordered it with. It could have an Allison automatic with five or six gears, it could have an Eaton-Fuller manual or automatic with 9, 10, 13, or 18 gears, it could have a ZF Meritor automatic with 12 gears.
Who invented the Semi-truck?
If the semi truck knocked on the garbage truck, yes.
For a North American truck, most of your average fleet trucks will run either a 9 or 10 speed transmission. Owner/operator and heavy haulers tend to have more gears - 13, 15, or 18 (15 speeds are a bit uncommon, though).
There'll be a panel inside the door frame which has the VIN number on it. The VIN will also be on the truck's registration.
A vehicle with 18 wheels is commonly known as a "semi-truck" or "tractor-trailer."
Semi-articulated
There is no prefix in truck.
Tom Nelson invented the semi truck in 1945
The chassis of a semi truck.
Alexander Winton, in Cleveland, Ohio invented the semi-truck in 1898 and sold his first manufactured semi-truck in 1899.
its a semi