Please see response from manufacturer, thanks!The difference between the two parts is the input hub of the gearbox on the motor side is a different size. RM142-89 is meant to mount to a 28 mm shaft diameter while the RM142-92 is meant to mount to 32 mm shaft diameter.The actual difference between the parts is a hub sleeve inside the hub that can be removed by hand at a customer’s site and a new one installed. The hub sleeve for RM142-89 is 05-113-336-19.Based on the serial numbers on the gearbox this goes back to 3 parts shipped on PO 804 D 24318 / SO 1958313.Can you confirm how many gearboxes are incorrect and where I can ship the correct sleeves to?