Actually they are still excavators with more guarding and a little different carbody.
Typical package build up includes high and wide undercarriage, swivel guard, full length standard or forestry rock guards, reinforced front idler pockets, bottom rollers for top rollers, many times heavier recoil spring ratings, full under-house guarding, right corner log guard, hard doors for the pump and radiator compartments, eighteen inch solid cab riser or forty eight inch hydraulic tilting cab riser, full cab guard, heavy duty bucket, forestry hydraulic link thumb and usually some sort of extra lighting package.
What they generally are is a logging shovel build up without the logging front.
These units came about because the rules for building roads in the woods changed to prevent spoil from being pitched down the mountainsides by dozers. Basically if you have a cut you have to haul the material to storage and then use it for fill somewhere else. The excavators took that job away from the D6 and larger sized dozers. As you can see from all the posts in this thread, these are extremely handy machines for road building in the woods.
