DIAGNOSIS A loud mechanical grinding or clicking from the drive area, especially when you first start moving, usually points to a problem with the drive belt or one of the drive motor input shafts.
FIX Start by inspecting the main drive belt. 1) Park on a flat surface, turn the key off, and remove it. 2) Lift the deck to the highest cutting position for access. 3) Look at the belt that runs from the motor to the transmission pulleys under the seat. Check for severe cracking, missing chunks, or if it's jumped off a pulley. 4) If it looks damaged or off-track, you'll need to relieve the tension from the idler pulley to remove and replace it. Refer to the belt routing diagram under the seat.
IF THAT DIDN'T WORK If the belt looks fine, the noise could be coming from a failing bearing on a idler pulley or a drive motor. With the key off and safe, try manually rotating each idler pulley by hand—they should spin smoothly with very little play. Any roughness or grinding feel means that pulley assembly needs replacing.
HEADS UP Don't ignore this noise and keep mowing. A failing belt can snap and potentially cause more damage, and a seized pulley or motor can lock up a wheel unexpectedly.