# Hydrostatic transmission testing tip



## veeguy (Jun 9, 2014)

I have a used Simplicity 7016H that I want to repower, but I have never seen it operate. I wanted to verify that the Hydro transmission worked before investing in a new engine. I took some pictures of the job that might help out others facing a similar problem.

I made an adapter to drive the bevel gearbox. The gearbox input is a fiberglass flex disc, so I used a 3.5" piece of 1" wide by 1/8" mild steel. I drilled a center hole to fit an old 3/8" drive socket, then drilled 2) 3/8" holes for the bolts that drive the flex disc.

I brazed the socket flush into the center hole- drive end out, then bolted the adapter to the gearbox's flex disc. I used socket drive extensions to run up to the original engine location. I then used a 1/2" Craftsman drill with a socket drive adapter chucked up to drive the extension to the flex disc. I used some plywood and 2X6 to shim the drill to the right height, then used a ratchet strap to hold the drill in place. I also drove some 3" drywall screws to keep the drill from shifting side to side or slipping rearward.

I jacked up the rear end of the tractor, fired up the drill and after a few seconds to "pump up" the system, I was able to run the hydro in both forward and reverse at varying speeds. 

The drill only runs at 750 RPM wide open, far short of the 3600 RPM an engine runs at, but it did the trick. I put a little resistance on the tires and the hydro develops enough power to turn regardless of resistance. I wouldn't run the drill for an extended period, I'm certain it would burn out, but a few runs of about a minute each was OK.

The last picture shows the transmission "bypass" with the "poppet buttons" popped up. I ended up disassembling the bypass valves. It took some Kroil and contact cleaner to free them up, that's what 3 years of sitting with the lockout pushed will do!

I realize that this isn't a 100% valid function test, but I feel a lot better shopping for a new engine now.


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