</font><font color="blue" class="small">( No problems on flat ground. The brake is not on. It just seems flaky sometimes. Also, I can't climb much of any hill in high range, even w/o the deck running, no attachments. Maybe I expect to much. )</font>
Sure seems like something is not right. From not to bad to worse: could be low on hydro fluid; clogged or defective air breather on the trans/hydro case; hydro relief valve stuck open or otherwise not allowing full pressure; bad hydro trans; or something adding a lot of drag.
When you can't move (like up a hill) do you hear a loud wine from the hydro ? If you do, it could be something dragging or a bad hydro. If you don't hear it it could be a bad relief valve for bad hydro.
In any case it should be under warranty, so have the dealer take care of it.
paul