How do you downshift an Eaton shifter?

Depends on what model it is. Eaton makes both synchromesh and unsynchronized transmissions. The synchromesh transmissions (6 and 7 speed) shift like a regular car or light truck transmission.. push in the clutch, downshift. Unsynchronized transmissions, you take the transmission out of gear, rev the engine up the appropriate RPMs, then push it into the next gear down. This requires you to hit the RPMs right.