Bstar makes a good point. The sprag clutch in your torque convertor could be slipping. This happened to me the first time on an MA60. Perkins 4.236, low power. Machine had about 10,000 hours on it. The owner/ my boss was sure it needed an engine. He allowed me to contact White and discuss the issue. The support tech told me to go into tilt relief and if the engine could overcome the pump and speed up to call him back. When I called h again he had me stall the truck against a pipe in the concrete and compare the stall speed against a sister machine. There was an obvious difference. The convertor was locking up about 800RPM, much too low to make any power. We replaced the convertor at customer location and the machine pulled great! Man, do I NOT miss those trucks!
Steve