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HerbP

hydro delay or lurch ...

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HerbP
Not sure how to describe this as I'm not sure how a 716H _should_ behave. I know how my 720 behaves but it's a different beast... I was doing some searching and came across a post discussing freewheeling valves which piqued my interest but the symptoms I'm seeing are not really consistant with what I think those valves do. So this is in regards the 716H I just bought a month ago... I've fallen in love with the little guy already but the hydro behaves quite differently from my 720... It seems I have to move the lever fairly far in either direction to get the wheels to 'engage' and then when they do, it's a sudden lurch. If I'm trying to perform a tricky adjustment, it's almost impossible to get the tractor to move 'just a little'... However, the tractor will creep when in neutral and will slowly crawl over practically anything used to block the wheels... If I nudge the lever forward or back within the neutral position, I can get the tractor to change the direction of the creep but never really stop... Also, the other day, I was trying to push the tractor backwards by hand a couple feet or so to clear the garage door and it would only move about 6 inches and then lock up; presumably because the hydro was engaged or something. Should I be able to move the tractor slightly without starting it? When I bought the tractor, I checked the play between the engine output shaft and the mid-PTO and there was none, at least no discernible play... So I'm fairly certain that whatever's going on is in the hydro valving or something... So this is a two part post... "What's normal for a 716H?" and "What might be wrong?"

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OrangeMetalGuy
If you look at the linkage (under the seat pan) where the control rod comes back, there is a rounded piece (think a section cut out of a pipe) that the control rod attaches to. As the rod moves front to back, the position of the round piece changes (it rotates). There is an offset groove cut into this rounded piece, and inside that should be a plastic piece attached to the end of the control arm on the Sundstrand pump itself. I would bet the plastic piece is either gone or dirty/bound up. Try to lube the linkage and see if that helps. If the plastic piece is gone, you will need to get another one.

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MysTiK
quote:
If I nudge the lever forward or back within the neutral position, I can get the tractor to change the direction of the creep but never really stop...
If you don't have it already, you simply gotta have the AC 700 SERIES manual - at Simp/Manuals insert 1690211 to get that manual. It's a great manual. ("manualpage 39") "Trax w Hydro Trans" and read all about it. OrangeMetalGuy makes a good point about the little red nylon roller in the CamPivotShaft /PumpControlArm /PumpControlArm Roller (see pix in manual) (pix clarity improves at zoom 150-200%). If the roller is there, and if it is still round like it should be, then that's used for the MACRO ADJUST for neutral creep, but there's another "jam nut" for MICRO ADJUST - also explained in manual. In doing this it's pretty finicky; but will get you close, if the MACRO is close to CENTERED POSITION. But the real "TWEAK" is the MICRO ADJUST - it's touchy, but it works. Clean the parts first w wd40, etc. But centering the roller is important - note you can use that to control max speed forward or reverse - i.e. if it's way off center, either forward or reverse is limited or maxed out. When I broke my hydro lever, the freed linkage defaulted to reverse and the roller was in it's highest point in the cam. So high in cam is reverse, low in cam is forward. You can see that if you operate the hydrostick. But yeh, the roller flattened out or gone will mess up everything. Mine is still ok. (It's hard to see it to assess it's condition). I have similar symptoms with general operations /sensitivity basically. On mine it's a delay in the linkage somewhere, and I have not found the magic lube point yet. I have cleaned the spring cages and lubed what seems obvious. But I am ok for slow speed operations in tight areas - there is a delay overall, any position. I get used to the delay, about 1 second or so. For mowing speeds, it's several seconds before the linkage catches up to what the lever position is calling for - and I can feel mine gradually pickup to the speed I "set". But fine tuning by lube has not worked yet; there's also some old articles about adding washers to the spring cages - haven't tried that yet. There isn't much to the linkage. Binding somewhere may be an issue. Replacing the roller may be the thing - but I can't see that doing it for delay issues. The main bolt for the MACRO adjust allows some flexing of the linkage, and I wonder if that's the problem. Overall I am getting used to the delay, learning to work it - set stick too far, then back off, stuff like that. In emergencies, it responds quickly with maybe an exaggerated command movement. I'm used to it. hope that helps - get that manual sm03

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MysTiK
Also possibly related - vague feelings in the hydro stick - preceding breakage of weld at bottom of stick. My adventures with broken hydro stick - the vague feeling preceding the break lasted for months. Lots of pix of the parts involved in that. http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=121508&SearchTerms=hydro+stick+bust

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D-17_Dave
The Sundstrand pumps have a spring detent dampener in the linkage. The cams get rusted and the springs get weak and this allows the linkage to jump. Most people take a couple of wire ties and lock the spring out so it's solid. This will at least tell you if the problem is this section. Of course the linkage needs the above mentioned bushings and such. You also could have a sticking clutch pedal and pulley due to the clutch doesn't get used much. This will allow the belt to lightly slip and make a hydro jerky. Also could have a stopped up and or the wrong filter on the hydro.

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colincox1
I had the same lurching problem, cleaning and lubing the linkage work for me, I used air compressor to clean, and wd 40, and now spray every month.

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HerbP
Thanks for all the responses folks. I checked out the linkage this weekend and it seems fairly solid and unsloppy from handle all the way down to the little red nylon roller. Moving the handle translates instantly into movement of the cam on the roller. On startup after a week of sitting in the cold, I moved the lever slightly forward, and waited. It took a good 5 or 6 seconds before the tractor started to creep and then it started to creep and got steadily faster. Once it was warmed up, it responded much better to the point where it would move forward/back by just moving the lever back and forth in the neutral slot. I assume at this point the problem is strictly related to fluid/filter/pump/motors... Attached is a photo I took while it was running in case someone sees something obvious. While the tractor is running, the loose washer on the far left jiggles around on the shaft and makes an annoying noise. I haven't looked to see what it's attached to but it looks like it wants a spring between it and the adjustment nuts?


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D-17_Dave
Check the rubber lines going to and from the filter base for dry rot as a pin hole will allow air into the charge loop and can cause a delay. Other than that you likely have moister in the filter or the wrong filter stopping the flow from being full flow as needed.

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HerbP
Well, I have noticed some dribbling of hydro fluid on cold start (twice now, once when it came home on my dad's new trailer deck)... So perhaps there's something to that. The clutch pedal seems to operate correctly... The tractor has an electrical issue when starting so I push the clutch in to start and then release when the tractor is running and I can hear the hydro start when I release the clutch pedal.

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D-17_Dave
You here the pump start to turn,,,,, As the pump increases speed it builds pressure. The more resistance the more drag on the belt. If the belt is not good ad tight from maybe a sticking linkage from a binding clutch, the belt can slip and not provide proper pressures or response. If you look at the linkage under the seat pan there should be a couple of nuts jammed together on the linkage rod coming from the clutch pedal. If these nuts don't have at least 3/4" of play between the slide the rod passes through then the clutch could be holding the belt tension and not getting you full power to the tranny.

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