No its not like a jake brake. The multipower system is a shift on the go system that you do not need to use the clutch when shifting. It can be used to start out in low and shift to high to increase forward or backward speed. It can also increase pulling power or slow the tractor down when needed when shifted from high to low. The internal gearing has an over running clutch that will allow the tractor to freewheel downhill when in low. In high multipower this over running clutch is locked by a hydraulic clutch and will stop the tractor from freewheeling and allow engine braking. Its a complicated system to explain and there is more to it that I can't explain but this is the easiest explanation I can give you right now. Not all TO35s have multipower.