A control system for controlling engagement of a first and second transmission of an all-wheel drive (AWD) walk-behind power equipment unit such as a lawn mower. The control system may include a mechanical load balancer to split an input drive force vector into two output force vectors. These two forces act upon associated first and second connection elements coupled to the first and second transmissions, respectively. One transmission may include a resistance element selected to sequence engagement of the first and second transmissions so that both transmissions begin driving their respective wheels at or near the same time even when the wheels associated with one transmission are more heavily-loaded than the wheels associated with the other transmission.