656 Hydro Problems

I recently bought a 656 gas Hydro tractor and have found it to have some problems that may or may not be major. I found this site and I'm hoping someone here can help me. The first and main problem may be with the Hydro itself as the guy I bought it from said it was weak in high range. He said they had the tractor since 1989 and have only used it as a loader tractor for which it has never given them any trouble. He said the hydro was weak already when they got it but it worked good in low range so they did not do anything to it. He said they had never changed the hydro oil or filter because of the low hours they put on it. (Total hours on the meter show a little over 5,000.) I changed the filter but not the oil yet as it looks pretty good. Because of a badly leaking cylinder on the mower lift I have had to add about 5 or 6 gallons of oil during mowing so I am probably mixing two different brands of oil (it had Cenex oil in it and I'm using a generic farm store oil that supposedly meets CIH standards). The first problem I had is that after mowing hay for a while in the road ditch I turned up the ditch and the hydro started to slip and I had to back down and climb the ditch at an angle. The hydro is definately weak in high range as it will only pull the tractor itself on a faily level plane but starts to slip on grades. In low range it works fairly good if I keep the oil level full and don't go too fast. Works wonderful for mowing and square baling. I have read all the posts on this site pertaining to 656 problems but would appreciate any recommendations any of you can make as to where to start looking for problems before I go the route of replacing the hydro. The tractor really runs nice, has excellent rubber and other than the slipping problem is in very good shape so I hate to junk it. I already adjusted the foot/inch pedal to get it away from the platform but I don't think that was causing the slippage. The partsman at the local CIH dealership said something about a forward and/or reverse valve that might be part of the problem? He also mentioned a possible charge pump issue? I'm not a mechanical person but if I have some recommendations of where to start I can find the right people to work on it. I plan to have the flow rate checked ASAP as that is something I have read about in several threads on this site. From there on I need advice. Thanks for anything you guys can tell me. I'll have more questions later about the remote hydro system but will start a different thread for that. tlk

ps: The tractor will only be used to mow and square bale about 20 acres a year. The rest of the time it will be used as a loader tractor to feed a couple of horses and push a little snow. Probably will get used less than 100 hours a year.

Get the tractor good and hot.

Take it out to that same ditchbank and see if the tractor will climb out of the hole in REVERSE Hi range without any slippage(it should).

If so, you just need a good tune-up on the ol' heifer.

Let us know what kind of power it has in reverse and I can send ya pictures of the repair.

Allan

Thanks Allan, I was hoping to hear from you. I will have to find some way to get her good and warm and try that. I'm done making hay and don't have any field equipment so I'll have to find something else to pull. Will driving it around my housing development in high range for a while do for warming it up? The temp gauge does not work so I don't know how warm it is running or maybe that's not the warm you are talking about. That's one of the other small things I need to fix ASAP.

Oh heck yeah,

Drive 'er around the block and then go see if that reverse is strong or if it slips also.

Doesn't take much running to warm that hydro up. Oil gets hot in a hurry. :>)

Pay particular attention to the way it pulls. It really ought to "dig" up that ditchbank in reverse.

Allan

Did like you said and ran her around the block a couple of times. First time around in hi range she went up and down the grades just fine. Second time around she slowed down pretty good up the steepest hill and the third time she stopped halfway up the hill and started squalling like a baby walrus. Went down the ditch and turned around and put her in reverse hi range and she backed up the ditch without any hesitation. Acted like there was nothing to it. Wouldn't go halfway up the ditch in forward hi range. Is that good news or bad? Checked the tanny oil and it is a bit overfull. Is that a problem?

No squealing noise whatsoever in reverse?

Allan

Not a peep. Backed up the ditch like a gear drive tractor. Had the lever all the way back to the highest speed in Hi Range.

Pard,

This is just an uneducated guess. I'm an old man but spent my life working on hydraulics and have been thru what you're facing a few times.

We've got one of two or three possibilities going on here. The problem "could be" up at the control head, but I kind of doubt it. However, there is a procedure to check which is giving you the headache, be it the control head or the transmission itself.

Better guess tho:

Either there is a crack in one of the small feed lines at the forward pressure regulator or forward check valve down in the transmission

OR

And more common, they normally just beat the heck out of those pressure regulator and directional check valves......especially, in forward range. Further, the "fails when hot" thing sure points at the valves.

My email is open. If ya want, shoot me an email and I'll send you the pictures of the repair.

Allan

Allan, sent you an e-mail. I think the logical place to start would be the check valves as you suggested. I will have to have the dealer order the parts as if I remember right he said they do not keep parts on hand for those older tractors. Can you give me a list of what needs to be ordered so I can take it to the dealer tonight after work and have him order what will be needed? I'm taking a wild guess that replacing the valve would be much less involved than trying to get to the feeder lines so if that's the case I will start there. If it's easy to get to those lines maybe I can check them before replacing the valves. What do you suggest?

"If it were my tractor", I'd replace both the pressure regulators and both of the check valves down in the center section.

But listen, we're talking about a $1,000 gamble here to buy those valves.

There is a somewhat "involved" procedure to check exactly what is going on with the old gal, but I'll just bet it is leaking by that forward regulator. It is what they do. Happens time and again.

Bad news is that if you replace that tranny, it's gonna end up costing you $5K. So, maybe the gamble is worth it?

To verify, a guy can exchange the two sets of valves from one direction to the other and the problem will follow by slipping in reverse instead of forward. Heck of a lot of work tho. :>)

All the piping has to be removed just to get at the valves. But again, kinda "doubt" you have a cracked line.

Email hasn't came thru yet.

Allan

Does the tractor need to be split in half to replace the regulators and valves or can you get to them through the side plates under the platform? Is it just as much work to replace both regulators and valves as it is to replace just one? If I have to split the tractor to replace one I sure would do them both at the same time rather than have to redo all the work again to do the other later on. Are there any places that sell parts at a discount or is the dealer the only source?

Oh heck no; no splitting involved.

The hardest part of this repair is draining the silly oil. Very easy unit to work on, but ya gotta have yer wits about you.

I just didn't want ya hollarin' at me if we "jump ahead and assume", then are wrong.

There is a step by step way of telling exactly what is going on. I was gonna email you my phone number so that I could explain better.

Darned email still hasn't came thru?

Allan

Allan, I resent the e-mail just in case I did something wrong the first time. Hope this one comes through. If you give me your number let me know what time would be convenient to call. I get home from work about 5 pm weekdays but will be off all day tomorrow and home all weekend I will try to match your schedule if possible. If I can try your check procedure before I tear into the tractor it may save me some money. I will hold off on ordering the parts until we hook up on that. Let me know if the e-mail comes through this time.

Reverse only works in the same range as the lower part of the forward speeds. If you only have problems with the lever push to the forward half of the slot then working in reverse really doesn't tell you much. The lower half of the forward slot and reverse move only the hydraulic pump to control speed. The upper part of the forward slot changes the hydraulic motor displacement to very the speed.

The first thing you should do is get a couple of 1/4 inch steel JIC caps and cap off the two lines that come out of the transmission. That will separate the external part of the system from the internal parts. If everything works OK with the lines capped off the problem is in the external controls. Be careful though because with the caps in place the Foot-N-Inch pedal will no longer work.

One other thing that that Allan didn't mention that may be causing the problem is wear in the forward slot so the the lever is not kept far enough to the side.

Doggone it!

I think I entered the wrong email address on that other post.

Try responding to this post and I'll bet it comes thru.

Sorry 'bout that.

Allan

Thanks Owen, I"ll see if I can figure out which two lines you are talking about and try that. I read something on a previous thread about slot wear but the guides are so tight I can"t move the lever from side to side anywhere except the slot where it moves back and forth from reverse to forward. Is that the side to side wear you are talking about? I"ve tried moving the lever sideways but there is no free play. Can you be clearer about that sidewise wear. Also, if I cap those lines are you saying that the hydro should not slip in hi range anymore if it is still good?

Capping the lines off at the transmission helps you determine if the problem is upstairs in the control unit or down in the transmission itself.

If the capping of the lines should by change CURE the slip, then the problem more than likely lies in the capsules in the hydraulic control unit above the battery.

Allan

I may be done working on the tranny for a while, I pulled a major boner last night when I was trying to replace the old heat gauge. I took the exhaust pipe off the manifold to get at the thermistat and brass tightner nut easier and ended up dropping the nut and thermistat into the exhaust manifold and can't get them out again. Don't ask how I managed that. May have to take the exhaust manifold off to get them out and that could be like brain surgery for a guy like me with three thumbs. Can't believe I did that. I'll start on that this morning right away but unless I can figure out how to get those things out of the exhaust manifold without removing it I'm in for a big job. I'll probably have to start this thread over again when I'm back to the tranny problem. Later.

The two lines are the ones that come out of the left side of the hydro housing near where the control rod goes in. By using the caps you can quickly determine if the problem is internal or external.

With the caps in place the spool valve that the sideways movement of the speed lever controls is no longer in the circuit. Neither is the Foot-N-Inch valve. The only control left working is the forward/reverse lever. There is no way to stop the tractor except by moving the speed control lever. Try this only when you are outside with plenty of room around so you don't run into anything. If you must do it inside a shop be sure to raise the rear wheels off the floor so you don't hit anything.

The high pressure relief valves are pilot operated valves. They are located the the hydro center section but are controlled by the Foot-N-Inch valve. They are designed to open at 5000 PSI but since they are pilot operated you can push them open by hand when you have them out. With the caps in place they will not open unless the jumper line between the relief valve and the housing is cracked.

hey don't stop now was tring to learn something about a hydro.

Ok, I think I follow you, however I'm not sure what sideways movement you are talking about in the spool valve? Also how will I know if the hydro slips if I jack the wheels off the floor? I need to have the tractor under load to find that, don't I. I managed to get the exhaust manifold off and back on so I'm back to work on the hydro-nice of the previous owner to only hand tighten the bolts on the manifold. I thought it would be a nightmare getting them out but they turned right out. Had to run to town to get a new manifold gasket so I picked up some 1/4" caps for the oil lines however I got pipe thread caps and it looks like these on the tractor are different so I'll have to make another trip back in tomorrow. You said the Foot/Inch pedal won't stop the tractor with those lines capped, will the forward/reverse lever stop the tractor or do I need to be quick on the brake? I have the mower hooked up to the tractor now so I'll have to try your line capping advice next week and start a new thread when I get the results. Thanks.

Allan, just wondering if you ever got my last e-mail?