I had my hydro and front motor rebuilt because they acted weak to me. One of the problems I had and now still have is the ground speed changes dramaticially going up hills and down hills. When going up it slows down even with peddle floored and then going down hill it will just race. I did n't send in my charge pump or the rear motor and I did change the oil and filter. Before I sent in the parts for rebuild I checked the charge pressure and it was at spec. The travel pressure should have been 6000psi and I had 3500 so figured that was the problem. Any ideas?