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wddjr

A/C 712S PTO Clutch Problem--Advice??

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wddjr
A while back the hub of my cone clutch got "eaten up" because the nut that holds the clutch plate on the pully shaft loosened up on me. This condition caused the center of the clutch casting to get enlarged. So, I picked up a new clutch (#174862) for $50. I went to put the new clutch on and much to my surprise, when it it torqued to 70 ft/lbs, there is no freeplay between the pully and the clutch. A close inspection of the old to the new clutch revealed no differences. The castings and the linings appear identical. When 70 lbs is put on the clutch retaing nut, it seats the clutch casting against a retaining ring that is on the pully shaft. Unfortunately, this means the clutch & pully are fully engaged even though the pully is in the disengaged position. Anyone ever have this happen? Could the plate (i think they call the part a "disk brake") that pulls the pulley to the disengaged position be worn out so that the pulley spring never gets fully compressed? I'm baffled at this point :) Thanks in advance for any input or advice!

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HubbardRA
I switched the clutch on one of my tractors and also had this problem. Fixed it, but don't remember how ?? I also have another tractor that I can't keep the nut tight on. I have tightened it at least three times when the clutch started slipping. I have heard that the nut should be replaced whenever it is removed. How did you hold the shaft, so that you could place 70 ft-lb on the nut? Just wondering. I put a wrench on the pulley nut on the opposite end of the shaft. Figured that would put the torque on both at the same time. There should be a better way. Hard to take them loose this way. Maybe a wrench on the driveshaft flange?

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tillerman
I had the same thing happen to me on my 917. The nut came loose while tilling. The tiller stopped working so I stopped and found the nut luckily. When I torqued the nut the same problem you had. I got some loc-tite and put it on the threads and loosened it to where it worked right. That's been 2 years now and it has worked good and stayed on. Richard

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2burning
I had that happen to my 716H, the nut came loose, the clutch wore into the nut, and the key way was loosened way up :0. I ended up buying a new clutch, but when I put it on it tightened up just like yours. I had to adjust (tighten) the linkage on the engagement linkage to allow for the new lining. Then it was ok. I had to use the special locktite product to put into my keyway, and I used normal locktite to on the shaft to try and help hold the thing together. One thing I do know for sure, if the nut is not tight (not just held in place with locktite), then the load will be placed on the keyway and it will not last as long as it should. You have got to have the load going through the clamping force of the nut, not the keyway.

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wddjr
Thanks 2burning. Our experiences are identical and I agree that clutch must be fully torqued down 100% or that key is going to start deforming quickly. The real problem is that I can't adjust the linkage enough to get any freeplay between the clutch lining and the pulley. The pivot assembly is actually hitting the side of the frame now when the lever is in the disengaged position, so the pully can't come in anymore at all. I think what might be going on is the disk brake (not a good name for the part) is worn so the pulley is not as far in as it normally would be when the disk is at its proper thickness. Another way to put it is: the surface where the pulley rubs the pivot assembly when you disengage a running PTO is worn thin. I guess it is like a disk brake b/c is stops the pulley from spinning when you disengage. Anyway, you can't see this unless you pull off the clutch, pulley, and pivot assembly. I'll do this over the weekend and see if this theory holds any water. If we can only get a nice weekend in New England :)

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Al
Hi, The most common cause of this problem is the retaining ring behind the clutch plate pushing out of the groove and the clutch being able to go in too far. If you look at the back of the clutch plate, you will notice that there is a recess there. When the retainer is in the groove it only is 50% in the groove. When the clutch plate is installed the recess goes over the retaining ring and holds it in the groove so it cannot come up and out. Then the tighter you tighten it the more it holds. If the ring is slightly distorted when you put the clutch plate on the distorted part is not completely down in the groove on the shaft. Since it is raised up slightly instead of the plate going over the ring, the ring contacts the plate outside the recess and just pushes it out of the inner groove and it just slides in on the shaft and lets the clutch plate go too far in. The same can happen to the retainer in the differential. Having a washer etc over these round rings is what stops them from being able to slide out up out of the half round groove. When these clutches fail prematurely, the bushing in the bearing in the pulley is usually bad and the shaft that the pulley slides on is usually worn. This lets the pulley essentially roll around the shaft and the part that goes in the clutch plate is constantly slipping in and out as the shaft turns, like a constant velocity joint. This wears the clutch lining because of the in and out slipping action on the lining. Al Eden

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wddjr
Thanks for the good info Al. Actually, the clutch plate retaining ring is engaged in the groove and is brand new. The clutch plate does snug up against the ring when I torque the clutch retaining nut to 70lbs. However, after tightening down the nut, the clutch plate and pully are fully engaged even though the pully is in the fully disengaged position. And there is no way the pivot arm linkage can be adjusted in any more b/c the pivot arm is hitting the frame of the tractor.

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Al
HI, Look at the pivot points in the release mechanism. I'll bet they are wron off at about a 45 degree angle and the holes are all egged out. If so replacement is the answer. However you might get by for a little while by grinding off the back side for a little more travel. Best shot replace it. Al Eden

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