The older 6055's had a different propeller (pre 2008) these would click because the prop had free play on the plastic shaft of the magnet. I would first try the prop from your other pump, if that solves it, a new 6055.700 drive unit is all you need. If it doesn't then the disk should be changed and 6055.700 and 6055.740 should be ordered, these will solve it for sure.