Genuine Hydro-Gear ZT-3100 hydrostatic transaxle ZL-KPEE-SNLC-3GXX. For left hand side (when sitting on the mower). Replaces Husqvarna part numbers 597561602 and 597561604 and Hydro-Gear part number ZL-KPEE-3NLC-3GXX.
Also available: Right side transaxle
