Why must the driveshaft be pulled up when checking backlash between gears on certain lower unit assemblies?

When checking backlash between gears on certain lower unit assemblies, pulling the driveshaft up simulates actual running conditions. This step is crucial because it ensures that the gears are meshed as they would be during operation, allowing for a more accurate measurement of backlash. Proper backlash measurement is vital for ensuring that the gears operate smoothly and efficiently without excessive wear or noise.

Simulating actual running conditions is particularly important since the alignment and spacing of gears can change slightly when under load. By adjusting the driveshaft, a technician can emulate the pressures and alignments that occur during normal operation, thereby obtaining reliable backlash readings that reflect how the gears will perform in real-life scenarios. This practice helps in identifying any potential issues before the unit is put back into service.