The Dumper is by far the largest land-based vehicle in GTA San Andreas, generally based on large off-road dump trucks used in large-scale earth moving. The truck resembles a cross between a 1970s Caterpillar 773, particularly the grille and cab, while other parts are from modern 773s. The Dumper is also only available in a Bluish gray, similar to the Dozer (blue-greenish). The Dump in GTA V is likely its sucessor.
The Dumper is a slow moving vehicle (with a top speed roughly similar to that of a Linerunner), but has the effects of the Monster truck. The "tipper" on the back can be raised up and down.
The default radio station in the vehicle is K-Rose.
There seems to be a glitch with the Dumper during one of the Quarry side-missions, where one will have to transport explosive barrels to Verdant Meadows. Upon raising the tipper and dropping off the explosives, the player will occasionally be rewarded with a four-figure Double Insane Stunt Bonus.
The Dumper, along with the Monster, has the "car-crusher" ability, which allows the vehicle to be able to drive over traffic, rather than through it.
If a car hits the back of the Dumper, it will be set on fire or badly damaged. However, if the vehicle is directly on top of a car, sometimes the Dumper will get stuck on top of the car. The car will eventually explode and the Dumper will also explode too.