You didn't say what year it is. Mine, a 2004, had deceleration that was remarkably quick - hazardous truth be told. A person that wasn't prepared for it might be unseated. A few months after we bought it, Kubota came out with kit to install that moderated the deceleration and made it tolerable.
I've never, ever, seen foam looking in the filler cap. If you are convinced/willing to assume the fluid and filters are correct, you might want to get the service manual, or go to the dealer and see if they will photocopy the trouble shooting section for the transmission.
Mine has a flow chart for trouble shooting the hydrostatic transmission on pages 2-S1 and 2-S2. The Charge Pressure relief valve and the High Pressure relief valve seem to be the cause of several problems. So measuring the pressure as suggested above is good advice.
There are also some mentions of servo piston adjustment and linkage adjustments.
At that point it resorts to the statement, "Replace Hydrostatic Transmission Assembly." At that point you will definitely need the service manual if you want to disassemble it and fix it instead.
Fitch
I've never, ever, seen foam looking in the filler cap. If you are convinced/willing to assume the fluid and filters are correct, you might want to get the service manual, or go to the dealer and see if they will photocopy the trouble shooting section for the transmission.
Mine has a flow chart for trouble shooting the hydrostatic transmission on pages 2-S1 and 2-S2. The Charge Pressure relief valve and the High Pressure relief valve seem to be the cause of several problems. So measuring the pressure as suggested above is good advice.
There are also some mentions of servo piston adjustment and linkage adjustments.
At that point it resorts to the statement, "Replace Hydrostatic Transmission Assembly." At that point you will definitely need the service manual if you want to disassemble it and fix it instead.
Fitch