185 Hydro - Gear Shifting Issue

I've slowly been rebuilding this mower I acquired, a 185 Hydrostatic. I had to replace most of the electronics, the starter, the fuel pump, and the carburetor - and now ... it works! Sort of.

I had it in reverse. As I moved from turtle to rabbit, it lurched and sprung forward, then it sprung back. The gear shifter was flapping away AS it was doing this. The gear shifter has always been loose.

So, is it the torsion and other gear shift spring? What's the easiest way to get to them? Is it removing the upper casing?

Thanks!
-Chris

Tried it again and was able to do a little driving around. The clutch lurches all around, too, while this happens.

Know nothing about your hydro but I can tell you this. It is not designed to be used in low RPM. Set the engine at full RPM then see what happens. All mowers are designed this way.

I'd suspect a belt problem first off. Maybe the idler pulleys are binding at the swivel point?