I have an older case 1816 uni-loader with the 16hp Tecumseh engine. It runs fine, but the left drive is extremely jumpy. I have changed the hydraulic fluid and filter, and I don't see anything loose or broken in the control lever or clevis. It works well when I am pushing or moving at full speed in forward or reverse, but when I try to do careful small movements (which is where I need this little loader the most) it is extremely jumpy mostly in forward movements. Any Ideas? Thanks!