Re: Locked up rear end

Posted by Samske on July 18, 2023 at 12:44:42 from (156.34.64.146):

In Reply to: Locked up rear end posted by Samske on July 16, 2023 at 08:41:42:

[quote="docmirror"](quoted from post at 11:45:50 07/18/23) [quote="Samske"](quoted from post at 04:44:40 07/17/23) . I was chewing spruce gum! but the tractor stopped moving forward and began to flex in the middle under my seat. A plastic shroud under my seat that usually is tight to floor mat is now up off mat by inch. Whole tractor is under loadfrom what appears to be something bound up. There were no sounds out of the ordinary like: poping, squealing, or breaking noise the energy just seemed to be absorbed in the tractor instead of rotating the wheels. Shut off immediately by key as soon as I felt the flex. It's been in the flex or stress position ever since. Unfortunately my back went out the next day and is just feeling better today. So haven't looked at it since. My knowledge of hydrostatic tranies is not great but I am a macanical person. I do most of my own work.[/quote]

Generally speaking, in tractor parlance, a hydrostatic trans has a clutchless connection to the engine. The engine pressurizes the hydro pump, and that pressure is sent to one or more double acting valves(similar to a spool valve) which sends hydro pressure to the various motor(s) to drive the wheel(s). Usually just one, but in the case of a ZTR there are two, one for each side.

I will assume there is one shift lever, and it has "N", "F", "R" for neutral, forward, reverse, and is a variable length lever throw for speed control. If the lever is still in the "F" condition, and the hydro system is still operating, you will not be able to start the engine with the load still on. Most hydro systems have a safety which only allows engine start in the "N" position, where the pressure on the spool valve is diverted back into the reservoir, and not directed at the motor(s).

1. Is your shift lever in a position OTHER than "N"? If yes, put it in "N" and the pressure will relieve from the hydro motor(s) which drive the wheels.

2. With the shift in "N", and the rest of the safety interlocks set like the brake, and seat will the starter engage? If not, there is an interlock problem, or shifter not in N.

3. If the starter engages, but the engine will not turn over and start, then the hydro pump is locked somehow, and you will need to mechanically disconnect the hydro input from the engine output to test the engine, and then the hydro pump.

As I stated back at the start, it sounds like the pump has become frozen for some reason. It could be a spool valve, but more likely the hydro pump is no longer willing to turn and create pressure.[/quote]

Thank you this is the info I'm looking for. Basically a place to start I will put in N and see if pressure releases. Will this happen fast or does it release pressure over a short time. Thank you very much. My next question would be the hydrolic pump on the side of engine is that only running the loader valve for the front bucket hydrolics or is there another pump at the rear of tractor in rear housing

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