What about 4WD? Bulldozers are tracklaying vehicles! There are very few wheeled bulldozers around and they are usually only operated on firm ground.
But if the bulldozer is track-type, it's absolutely unnecessary to power more than one wheel per track. Recent discussion about hydro-motors prob working against each other shows, powering two wheels on each side is a potential reason for trouble. Instead give it a well-designed tracklaying carriage. Bastelmike 20.1.2012