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Discussion Starter #1
Keeping in mind that this is my first hydro tractor, please overlook my ignorance in how our machines work.
First, I'm certainly aware that my brakes need a huge adjustment, but they just hold, when completely depressed. So keep that in mind as you begin to laugh, as this story progresses.
Last night at last light, I had one last mission to complete before calling it a day. I needed to tie a branch up, on my pear tree that is overloaded with fruit. I was going to do this enroute to putting the tractor up.
So, I pull the tractor up, right under the tree, and I put him in neutral and set the parking brake. He was parked on a very minor slope, not anything I would call a hill.
I was going to quickly stand on the fender pan, wrap a piece of twine around the trunk, and branch; wham bam, and done, then head to the barn.
Weeeellll, that ain't exactly how it went.
I hopped up, and just started to make my move, when suddenly I found myself Deere surfing away from the tree.
Freaky, and startling, but no harm, no foul. All ended well, the tractor came to a stop about 10 feet later, and I had managed my way to the seat.
The parking brake was still engaged, but needed a little more push to actually engage the pads with the drums, so that's just an adjustment issue.
The real question I have, is why didn't the hydro hold in the neutral position, with the tractor off?
Possibly just an adjustment or slop in the linkages?
 

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Jm, All manufactured parts have tolerances. As parts are used, they wear and the tolerances may not be as tight/close as they once were. The hydraulic motor portion of your drive has a case drain. This allows and fluid that slips past pistons to go back into the hydro case...the "missing" oil is then replenished by the charge pump. Even though the engine is running, with the hydro control in Neutral, no oil is being pumped into the hyd motor. When on a grade, the weight of the tractor "pushes" against the gears attached to the hyd. motor and tries to rotate the hyd motor. The oil in the internal lines prevent this until oil seeps out around pistons in hyd motor...it may also seep past 2 check valves. Once the oil in the internal lines is gone, nothing stops the tractor from rolling!

With a brand new hydro, I wouldn't expect this. But your 318 isn't brand new! What you experienced is "normal" for the age of your tractor...not fun, but normal!

Unless you're IN the seat, don't trust Neutral or the brakes! Running or not running, chock wheels after leaving seat unless of flat ground. Bob
 

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Discussion Starter #3
Jm, All manufactured parts have tolerances. As parts are used, they wear and the tolerances may not be as tight/close as they once were. The hydraulic motor portion of your drive has a case drain. This allows and fluid that slips past pistons to go back into the hydro case...the "missing" oil is then replenished by the charge pump. Even though the engine is running, with the hydro control in Neutral, no oil is being pumped into the hyd motor. When on a grade, the weight of the tractor "pushes" against the gears attached to the hyd. motor and tries to rotate the hyd motor. The oil in the internal lines prevent this until oil seeps out around pistons in hyd motor...it may also seep past 2 check valves. Once the oil in the internal lines is gone, nothing stops the tractor from rolling!

With a brand new hydro, I wouldn't expect this. But your 318 isn't brand new! What you experienced is "normal" for the age of your tractor...not fun, but normal!

Unless you're IN the seat, don't trust Neutral or the brakes! Running or not running, chock wheels after leaving seat unless of flat ground. Bob
Thanks Bob.
As usual, good information, and solid advice.
I need to get in there and go through those brakes, but I'm not looking forward to the stuck bolts and brake drums that I'm sure I'll find. As with most everything else on this tractor, not a bolt has been turned since he left the factory 30 years ago.
 
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