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CrestonM 
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Joined: 08 Sep 2014
Location: Oklahoma
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 Topic: Pulling a Hydrostat Machine
Posted: 12 Nov 2019 at 7:54pm |
I know in the cabs of Gleaner L/M and newer combines a decal says to disconnect the final drive couplings on hydrostat machines before towing. I know not following this will tear up the hydrostat, but what exactly will it do? What's going on inside the system when you do that? I've been told by a lot of guys to never attempt pulling one with the couplers connected (I will never pull one with them connected) Just looking for a better explanation when I'm telling others why they shouldn't do it. I've heard guys say they've moved dead machines 10' or so with the couplers connected, and should therefore be able to tow them that way, but I would l like to be able to explain what will happen to the system if they attempt that. Thanks!
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DrAllis
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Posted: 12 Nov 2019 at 8:06pm |
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Shifting the transmission into neutral will see to it the hydro suffers ZERO damage. The problem with towing it very far or very fast in neutral is the transmission will suffer damage from lack of lube oil. Disconnect the axle couplings and then there is no problem.
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LeonR2013
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Posted: 12 Nov 2019 at 8:17pm |
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There is not a pump connected that will pump oil through the gearing. Leon
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CrestonM
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Posted: 12 Nov 2019 at 8:57pm |
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Thanks guys. So, correct me if I’m wrong, but is the transmission pressure oiled by a pump then, and the pump not operating starves the transmission bearings of oil?
In my head I’m picturing a regular transmission like the gear drive machines have, where oil is carried by the gears. Is the transmission on a hydro F2 or similar machine not the same way?
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Dakota Dave
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Posted: 12 Nov 2019 at 9:32pm |
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When you drag a hydro machine your not hurting the grears but your killing the hydraulic motor. Without hydraulic pressure your forcing the motor seals against the motor housing some hydro drives wont turn at all and will drag the tires putting massive strain on the motor seal's
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im4racin
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Posted: 12 Nov 2019 at 9:38pm |
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We need to explain 2 different things. What happens to the trans and what happens to a hydro.
The trans(manual) Not sure how the combine trans works for lube but most of the time the output shaft is not in oil so it will not sling oil around for splash lube. If it has a pump it probably will only be on the input otherwise it uses splash from the lower counter shaft that runs in oil.
The hydro. The hydro is basically a swash plate and pistons for pump that you control the angle of the swash plate to control speed and direction. The outlet and inlets are connected directly to a similar type of motor with fixed angle of the plate. When you pull a hydro the motor becomes a pump and the actual pump is locked due to flat swash plate angle. The oil from the motor now acting as a pump has to go somewhere. It will go over the relief valve and then cause cavition on the motor swash plate. Cavition is basically air in the oil that can’t get away. That will pit the parts in the motor and pump when under pressure. Pitting will create a rough surface and chew up all the brass parts.
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jaybmiller
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Posted: 13 Nov 2019 at 7:20am |
It's one thing to drag any 'hydro' unit 10 feet totally different to haul ! Do what the good DR. says... and you'll be fine. When towguys haul semis they drop the drive shaft, same for cars. better to be safe than pay $$$$$$ for being in a rush-it won't matter. If someone say 'no problem', let THEM haul it and pay the bill !!
Jay
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor)
Never burn your bridges, unless you can walk on water
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DrAllis
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Posted: 13 Nov 2019 at 9:48am |
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When you drag a skidloader with the engine shut off, you are introducing twisting force directly into the hydraulic/hydrostatic drive motor. Some newer models have a park brake built into the motor, so probably no damage there, but older models without a parking brake built in them wouldn't like being drug around. A combine is a whole different animal with a gear transmission in-between the motor and the drive wheels.
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jaybmiller
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Posted: 13 Nov 2019 at 10:39am |
Sadly had a Warn overdrive unit DESTROY the 'sun' gear due to lack of oil.. it was NOT fun trying to remove it from the rest of the guts.... Hydrostatic riding mowers all have 'bypass' valves so you can safely push/pull/drag then ,though generally only short distances.
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor)
Never burn your bridges, unless you can walk on water
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CrestonM
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Location: Oklahoma
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Posted: 13 Nov 2019 at 3:25pm |
 DrAllis wrote:
When you drag a skidloader with the engine shut off, you are introducing twisting force directly into the hydraulic/hydrostatic drive motor. Some newer models have a park brake built into the motor, so probably no damage there, but older models without a parking brake built in them wouldn't like being drug around. A combine is a whole different animal with a gear transmission in-between the motor and the drive wheels. |
Dr, is this like what you're talking about? It's an old cotton harvester that is fully hydrostatic with no type of gear transmission. Just 2 motors on each drive wheel. How would you pull something like this without damage, being as there's no transmission?
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SteveM C/IL
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Posted: 13 Nov 2019 at 5:13pm |
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I'd bet NO! My zero turn has hydro motors driving each wheel. Can not move it by pulling without sliding tires. There are hex fittings to turn out 5-6 turns to tow. It then free wheels nicely.
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