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HubbardRA

Freewheeling valves - rebuilding

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HubbardRA
First of all, let me say that I placed this post in Show and Tell to inform members of my discovery, and the usefulness that I thought it would bring to others. I have no ties at all to this man, and have no reason to try and sell his products. I know that items like this should usually be placed in the Classifieds, but I placed it here in an attempt to make other members aware of this option when replacing faulty freewheeling valves. If there is a better way to post items such as this then please make me aware of it. Feel free to move it as necessary, but I think it should be left here for at least a few days so that others can be aware of the service. Many members have had problems with freewheeling valves on their Sunstrand hydro trannys and know that the price of replacement can be quite high. I was looking for a part for a friend of mine for a Cub Cadet and stumbled onto this guys posts. He apparently has started a business rebuilding the freewheeling valves, and he even sells a new valve that is owner serviceable. The prices are very reasonable $35 for a rebuild, and $80 for a new rebuildable valve. He also sells the kits so you can rebuild the valve yourself. Don't get confused when reading his posts. All of his pictures are of the Cub Cadet "automatic" valves, but he also does "manual" valves like are used on Simplicities, ACs and Deeres. These valves are directly interchangeable, except that the manual valves stay closed unless the release is triggered, while the automatic valves will open up when there is no pump pressure on the valve. This is basically just a difference in the internal springs within the valve and the automatic valve does not have a plunger coming through the top of the valve, like the manual valve does. What he does in a rebuild is use a lathe to machine off the end cap, then installs the required rebuild parts, then welds the end cap back on. The rebuildable valve has a screw-off end cap so that the owner can install the rebuild parts himself. Here are links to the "rebuild your valve" post, and the "owner rebuildable valve" post: http://www.ebay.com/itm/Cub-Cadet-Auto-or-Manual-relief-valve-REBUILD-SERVICE-/320670405175?pt=LH_DefaultDomain_0&hash=item4aa9721237 http://www.ebay.com/itm/REBUILDABLE-Cub-Cadet-relief-valve-All-Cub-Cadet-hydromatics-125-127-1450-1650-/220893918280?pt=LH_DefaultDomain_0&hash=item336e4db448

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n8in8or
This has me interested. I did a search on the forum for "freewheeling valves" and I didn't find anything so pardon me if I am asking something that has already been discussed.... What are the symptoms of a leaking freewheeling valve? I have a Sunstrand hydro in a 7016H that doesn't act right to me. When it sits for a while (a couple days), after you first start it, the hydro doesn't immediately respond to the stick when you move it. After you are moving, it doesn't feel responsive at lower travel speeds. Also, when I'm mowing at a slower speed and go up a hill the tractor slows down appreciably, but if I move the stick forward more there is plenty more speed available. This is with the engine at full throttle so the pump should be making adequate flow and pressure. It seems to me like there is a check valve of some sort that leaks down, but I'm not familiar enough with hydros to know for sure. Does this sound familiar to anyone? If it is the freewheeling valve then this sounds like a great way to solve the problem, thanks for sharing! Just to complete the picture, I have changed the fluid in the transaxle and replaced the filter with a new Simplicity filter. I just got the tractor this summer and didn't drive it enough before the fluid and filter change to know what it acted like before I did that. Nate

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HubbardRA
My tractor does not always "immediately" respond as soon as I start the tractor. I usually just move the control lever to forward, then to reverse, and back to forward several times before trying to use the tractor. I always just chalked it up as a leak-down that happened after sitting for a long while and figured there was a need to cycle the system to purge any air pockets in the system.

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MysTiK
I'm working on a similar, or maybe same, kind of thing. It's not a huge problem, I just want response, to my inputs, to be somewhat quicker. My symptom is that I move the hydro stick to where I should get the speed I want, and it moves, but slower than desired, and then eventually will increase speed to what I want - and the "what I want" is just from familiarity, or knowing what it usually will do. I can get immediate speed by pushing forward more; but then, same kind of idea, it starts going way too fast after some 10 second delay, so I have to back it off. Seeking an answer I found some old posts that say this is simply caused by the linkage under seat, and specifically the "spring cage" - rectangular with spring in it - being DIRTY. So, I cleaned it up with some WD-40, cleaning within the cage, and also the rod near the cage - and it might have helped; but I don't have it fixed yet. So perhaps I need to clean something else, or more of the lingage - not sure yet. Also, this linkage, and other parts, were all disconnected during a "splitting" of the tractor to perform a bgb, bevel gear box, repair. I had to reset the hydro linkage and control cam w the little roller in it, to offset "neutral creep" (forward creep or reverse creep while in neutral). So I have a bunch of things just settling in again. Also running a new trans belt. The hydro works fine, just this delay effect. And the neutral adjust got rid of the "creep". so that part is ok now. The delay continues. I might have created a "binding" of the control rod parts - just another idea. Maybe, recycling the system, for automatic purge would be good. Seems to me I pulled the vent tube open recently, for no real reason. That may have allowed some air in. And now that I recall, this is nothing new, it's seems it's more of an off and on kinda thing. But I will try recycle to purge. Sorry if this is confusing - I just think I might be in the same ballpark. I haven't had noticeable freewheel problem that I know of - I use freewheel when I need to nudge the tractor around in the garage. It works fine, goes up and down, seems good for engage and disengage. (warning - don't ever TOW a hydro - it kills it). .

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GregB
Nate, The "freewheeling valves" are on the top of the hydro pump. Brass hex head with a little piston plunger sticking out the top. These valves are made to release the pressure in the hydro so it can be pushed around without damaging the charge pump. When mine "failed" they actually got sticky and stayed in the down position. When they were stuck the hydro would not move tractor at all. I pulled it from the pump housing, soaked with PB Blaster, then used a small pin punch to free up the check valve ball inside. I guess with time the seals and o-rings, also get hard and could use replaced.

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n8in8or
Thanks for the reply Greg, I wasn't sure what the symptoms of a failing freewheeling valve are. It makes sense that it just gets sticky and won't pop back up after you've pushed it down. My dad's are sticky on his 916, but not to the point that they won't pop back up (yet). I did some Google searching and found something with a similar Sunstrand problem as mine and they were told that it was just time to have the hydro rebuilt. So I may be in the market for a new hydro. Ray has one for sale locally, so I may go pick that up from him after I get my bonus check next month. It's no fun when you can't go the speed that you want at low speed.

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MysTiK
I also had another possibly related problem when the pin at the bottom of the hydro stick let go. I ran a thread on it, made an overkill documentary photo op, had a lotta fun with it. The weld that holds the pin at the bottom of the hydro stick let go, almost, and eventually broke - causing zero hydro control. Things got extremely "vague" just before it broke. (long story, see link) http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=121508&SearchTerms=hydro,stick,bust

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n8in8or
Mine doesn't appear to be a linkage problem. In fact, today while I was working on adapting a trac vac to mine, I was able to push the tractor forward without the freewheeling valves depressed. I started it and drove it and after I shut it off I couldn't push the tractor. After I let it sit about 2 hours I could push it again. So I'm getting some kind of pressure leakdown, but I don't know if it's fixable by a component replacement or if it requires a full rebuild. I'll probably buy a good used trans and save this one for parts and may even try to rebuild it myself when all of my other projects are done in 2035 :D.

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HubbardRA
These units all have "manual" valves in them. Leaking down as most of you are talking has nothing to do with this valve. Most of the leakdown is within the pump and motor of the Hydro. The leaking in the valves talked about in the links I posted is around the ball valve and out of the vent hole. On our units that would be around the pin coming out of the valve.

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MysTiK
Leak down let's them move? That explains it.... I did an unexpected reverse exit from my trailer a couple of weeks ago. Trailer was slightly sloping to the rear. Sitting on the tractor, fumbling for the key, tractor starts to roll. :O Tried to start engine = FAIL -> whoosh -> down the ramp I went. I was amazed how calm I was - I did a simple J-turn and it stopped. If I had gone straight - could have been dead under the tractor. B) I've been haunted by this ever since - to the point where I might try to make the brake work. 8) A very strange experience. Don't try this at home. :D

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n8in8or
I guess it doesn't surprise me to hear that they all leak down, but since I have 2 working ones now I'm definitely noticing that one operates much better than the other. It's still usable, but it doesn't work as nicely as I want it to so I'll put it on the list of things to improve someday.

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HubbardRA
The automatic valves used in the Cub Cadets leak down as soon as the engine is shut off, since this is what they are designed to do. They close and then open each time the tractor is used. This is most likely the reason they tend go bad and start leaking more often than the manual valves. The manual valves may take minutes, hours, days, or weeks to leak off, or not at all. The leak off can also come from within the pump and hydraulic motor. It is hard to determine where the pressure leak off is coming from. Very few hydraulic systems will hold pressure for extremely long periods of time. This is why you never park a FEL or backhoe with the bucket in a raised position. It will go down slowly over a period of time, and very quickly if someone hits the control lever even though the engine is not running.

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n8in8or
Yeah, I suspect it's a problem within the pump and/or motor, but it just occured to me last night that I have the blown up hydro that came out of my other tractor, so it wouldn't hurt for me to swap the valves off of that one just to see what happens. My issue isn't with the hydro leaking down as it sits - that isn't a major issue, however the speed with which it leaks down is symptomatic of other problems. My main issue is that at high engine rpm but slow travel speeds the hydro is not very responsive and the tractor speed significantly slows down when going up a hill slowly (like when I'm mowing). This isn't right and the fact that this tractor leaks down when parked much faster than the other one that drives correctly seems to tell me that the problems are inter-related. My intention wasn't to hijack this thread so I apologize that this has gone on so long, I was mostly curious what the symptoms of a bad freewheeling valve were since it sounded like a slightly common problem. If I ever do some further testing and fixing of my existing hydro I'll start a new thread to report on my results in case it benefits anyone else.

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MysTiK
Another trick I read about, haven't tried it yet. People suggest add washers to the spring cage on the linkage. I've never understood exactly how that spring cage works. But I guess adding washers might improve deteriorating spring tension - kinda like "preload" on the spring, making it a little more lively. Sounds like something simple to try anyway. I guess some people have added a few washers at either end of the original spring. Nate, I really don't think a rebuild is the thing. (last resort). These Sundstrands are largely bulletproof. On mine, I'm still pursuing linkage cleanup ideas. I have also heard good things abut WIX filters, and esp. the one that's referred to as the LONG one, slightly longer. And some technical talk about it storing more fluid to offset tendencies to cavitation, etc. Also supposed to have quietened whine on some of them. Other brands good too; the emphasis is not on brand but on larger (remote) filter. I still think this is linkage stuff, from what's been said. Rebuild is no picnic, needs be clean clean; the info is available however. Sundstrand repair manual. Finally, trans belt, and it's idler - if it's slipping, due to tension or oily, then trans is irregular response. (downhill freefall, etc.) linkage, etc. http://www.simpletractors.com/club2/topic.asp?ARCHIVE=true&TOPIC_ID=17454&SearchTerms=hydro,linkage,clean,spring http://www.simpletractors.com/club2/topic.asp?ARCHIVE=true&TOPIC_ID=61280&SearchTerms=hydro,linkage,clean,spring filters, etc. http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=121686

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