Take the side panel off of your dash, and you will be able to see where the hydo lever pivots. There is a bolt that you can tighten to make the lever harder to move and stay in position. This should solve your problem.
The hydro shift lever doesn't seem to have a bolt as described. The lever's piviot point is centered on a pin that allows it to rotate freely. There is also a spring to pull the lever back to a neutral position.
There is some kind of a blade that goes thru a clamp type mechanism that can be tightened to put enough friction on the lever so it won't move freely. This is the best I can remember , hope it helps you.
