Husqvarna T540XP Worm Drive (Oil Pump Gear)

The Husqvarna T540XP worm drive is the small gear that turns the oil pump on the T540XP top-handle chainsaw. When it wears or strips, the bar stops getting oil, and a dry bar and chain on a climbing saw wears out fast and cuts poorly.

Signs the worm drive is gone

Hold the running saw over a stump or a piece of cardboard and rev it. A healthy oiler throws a light line of oil off the nose. If you get nothing, and the tank, oil hole, and bar groove are clean, the worm drive is a likely suspect.

These gears are plastic and wear against the clutch drum. Running a dry tank, a gummed-up pump, or a drum that has been on too long all speed up the wear. A top-handle saw that works aloft all day needs reliable oiling more than most.

Replacing it

The worm drive sits behind the clutch, so you will need a clutch tool and a piston stop. Check the gear, the pump, and the drum while you are in there. More T540XP and other saw parts are in power equipment parts.

Work on a cool saw with the plug wire off, and confirm the oiler is working before the saw goes back up the tree. Top-handle saws are for trained climbers working from a secure position.

If the new gear does not fix the oiling, look at the pump itself, the oil pickup and filter in the tank, and the oil line for cracks. Adjustable pumps should be set to give enough oil for the bar length you run.