Have a Cat V50D in which the transaxle has been rebuilt and the hydraulics have been gone through. It works great then it lacks power. Happens both in forward and reverse. You can push excelarator to floor and it either sluggish or will not move at all. If you hold clutch down and rev up engine for a minute then it will work great. Sometimes it will continue to work as it should and other times it goes sluggish or stops. Anyone have any ideas ??