Although it is normal for any vehicle to slow down slightly when ascending a grade, there are a few things to check if this seems to be excessive.

Begin by checking to see if the belt that drives the pulley on top of the transaxle is worn or glazed*. If the belt shows either of these signs it may simply be slipping under load and it's time to replace the worn belt.

If the drive belt seems okay or has been recently replaced, then the problem may be with the idler bracket and tension spring responsible for keeping this belt tight. Check for a missing, broken or worn spring and service as needed.

If these do not resolve the situation, the problem be with internal components of the transmission. Please consult the applicable service and repair manual or contact a local service dealer to have the unit professionally serviced.

HYDROSTATIC TRANSMISSION MODELS ONLY -  It is natural for a hydrostatic transmission to continually seek out an even pressure condition. As the resistance load increases the system will work proportionally harder to reach this neutral pressure state. A tractor moving UP or DOWN a grade increases these loads to the system. To retain a hydrostatic transmission in a selected speed we use a system of friction drag washers to hold the speed selector linkage in place under load. If the tractor begins to slip into neutral too easily under load, these drag washers may need adjustment or replacement. This procedure varies by model and requires specific tension. Please consult the operators or service manual for more information about this service, or contact a local authorized service dealer for assistance.