Lumberjack rear suspension is very hard rear suspension that has almost no give. It was originaly thought of as lumberjack a long time ago when people had broken rear suspension and they put lumber in to block it up. Normally you hammar a car and the rear suspension compresses, with a hard rear suspension the rear end diverts all it's energy to the rear but being it has no give, the energy is diverted into making the front end lift up ( wheelie ) . lumberjack these days is just really hard suspension, it is in no means sticking lumber in your springs, that is how it got it's name.