Clutch failure (AGAIN!) Ford 1100 4WD

[tosii2]

Russell,
The clutch disk won't move easily with the clutch pedal down, even adjusted to max out the forward distance of the throw-out bearing (eg, hit that hard stop I talked about). It WILL move, but there is definitely too much drag. I agree that I SHOULD be able to move it easily in these conditions. What I see happening between the disk and the plate is that I can see the plate move backward, however, the spring cushion between the wear surfaces in the clutch plate expands the disk thickness as much as the plate can move back. So I end up with a still touching pressure plate, disk, flywheel situation. With a new clutch plate and disk, the pressure plate will stand well off the clutch disk. This one did when I put it in; it doesn't any more.... I can't think of what would have changed in the length of time this clutch has been in surface other than that the release fingers of the clutch pressure plate have lost temper, or for some other reason, no longer lift the the pressure plate itself.

Relative to the 'does it stop'... as it is currently, in high range on normal ground, yes. in low range in any gear on a flat paved surface, not really; it slows down a bit in the higher gears (in the low range); the clutch is obviously dragging; the engine rpms can change without the ground speed changing as quickly. All this says to me it is dragging.

It won't shift without grinding at all currently. I CAN get it into gear (with grinding); before the last clutch job, the only way I could shift without a scary amount of grinding was to shut the engine down.

I realize this isn't a synchromesh transmission with all the behaviors that go along with that.

Thanks again everyone!

Terry

 

[jones6780]

I have never heard of a clutch disk expanding in thickness. The springs on the clutch disk take up shock from pressure plate release and rotation. Sounds to me as though you have pressure plate/release bearing problems. and I would lean toward pressure plate.

 

[tosii2]

If you look very carefully at the clutch disk as the pressure plate begins to rise off it, you will see (at least in the disks I had at hand) that the disk does slightly (maybe 1 mm or so?) expand in thickness; as part of the assembly that holds the 2 wear surfaces to the rest of the assembly, there is some built in 'spring' there. Take a plate you might have laying around and put it in a vice and see this action. I presume it is there to ease the clutch engagement and make the clutch less 'grabby'. You won't see this in performance clutches because they want that grab.
I totally agree there is a pressure plate problem; The question is why I have now blown through 3 pressure plates; all with the symptom of not being able to depress the fingers enough to disengage the clutch. Both of the old ones I have from previous clutch jobs will not disengage with the manual jig I made to simulate the throw out bearing motion whereas the new one I compared these with released easily (see earlier postings on this jig).
The question is what am I doing to cause these plates to fail in this way, or what is wrong with the plates?

Thanks for our thoughts on this!

Terry

 

[jones6780]

Can you post pictures of the failed pressure plate? With jig in place?

 

[tosii2]

I don't have any pictures now, but will take some when I tear it apart this time.

Thanks

Terry

 

[tosii2]

The thread isn't dead!
I finally tore down the tractor and am in the process of trying to figure out what is going on.
Here's what I have so far:
1. someone suggested checking the crankshaft end play; that is at about .012, which is well within spec.
2. Here is a picture of the fixture mounted on the clutch:

The bolt sticking up in the middle of the fixture is turned to depress the clutch plate fingers. The bolt presses an old throw-out bearing against the fingers. I use the number of turns from when the bearing first contacts the fingers as a measure of how far I am depressing the fingers.
3. Here is a picture of the plate and the disk edge on with no fixture attached.

On the left is the flywheel, then the 2 friction surfaces of the clutch disk (the flat spring joining them which also transfers to rotational force to the body of the disk is barely visible between them), then the pressure plate itself, with the clutch cover plate overall.
4. A photo of the disk on edge with the fingers partially depressed:

note how the spring between the friction surfaces has expanded and still holds the friction surfaces against the flywheel and the pressure plate.
5. A photo of the disk on edge with the clutch disk now free to rotate:

The gap between the disk and the pressure plate is visible.

6. The boss that the the release bearing hub rides on is currently limiting the forward motion of the release bearing; eg with the pedal all the way down, the hub is up against the boss. This is a hard limit that is designed into the tractor, so there is no way to make the bearing push the release fingers any further forward.
7. Through a series of measurements referenced from the mating surfaces of the engine and the bell housing, the release bearing is currently set to be riding on the fingers at rest (no free play there) and the release bearing can move forward .187" when the pedal is depressed.
8. using the fixture, I checked 4 clutch plates with the same clutch disk; measuring how far they need to be depressed to give .010" of free space around the disk when the fingers are depressed. There were 2 old plates, the current plate, and a new plate.
Here are the measurements:
-Old plate #1: 5 1/2 turns of the bolt -.423" motion
-Old Plate #2: 4 turns of the bolt -.308"
-current disk: 2 1/2 turns - .192"
-New disk: 1 3/4 turns. -.135"
Note that the current disk needs slightly more than the motion available from the actual throw-out bearing assembly.

I am going to quit here for now; I can add more details later if needed.

Thanks for any more suggestions anyone has.

Terry

 

[Hooked_on_HP]

Are you buying your clutch parts from N/H. I am wondering if the part # has changed a bunch of times and and now something is miss matched. Have you talked to your N/H service dept. to see if they have any ideas. I wish I could offer more help but like you I am stumped.
Bill

 

[tosii2]

Bill,
I am buying the parts from New Holland, the part numbers are the same as the ones in my parts manual, I believe (working from memory here, but will check in the AM). It is frustrating to have to tear this machine down so often!

I haven't talked with a service guy at NH about this; I don't have one real close, so do most of my business by phone or web orders...When I did the first clutch replacement several years ago, I did talk with the parts and service guys and all they told me was that they normally replace both the plate and disk anytime there is a clutch problem. Which is what I have been doing. I should probably try to see if I can get some opinions from them if I can get the time to head up there when they might have the time to think and talk about it.

Thanks for the thoughts!

Terry

 

[tosii2]

Some more data on the clutch linkages:
1. the fork has about .030 play at the slots in the hub that it rides in. There isn't a lot of wear visible, perhaps .005 worth.
2. the leverage in the cross shaft and fork works out to about 2.9.
3. the leverage in the pedal to the rod that moves the cross shaft is about 7.5.
4. the .030 play at the hub translates to .030*2.9*7.5 ~=.65".
5. The spec pedal free play is 20-30mm, or .79" to 1.18", so just the play at the fork-hub interface is a large fraction of the spec free-play. This gives nothing for other play in the linkage or for the actual free-play between the throw-out bearing and the fingers of the plate. (well, I realize that the play at the hub can translate to play at the bearing, but there won't be any force pulling the bearing off the fingers other than small variations in the fingers pushing the bearing back).
6. I am tempted to talk convincingly to the hub with a torch and hammer to see if I can reduce that .030 a bit and at least take some of that out of the equation. But I still have trouble thinking that the bearing sitting lightly on the fingers would cause the fingers to loose temper or whatever is happening!

Terry

 

[BernieBenz]

First I must compliment you on your applied logic, measurement techniques, and persistence. I don’t believe that your release fingers are deflecting if they haven’t turned blue. Look for a simpler problem and solution.

I have an ’87 Ford 1120 which I suspect may be quite similar. At about 750 original hours I was having clutch release problems similar to yours and out of adjustment range. Upon disassembly and inspection, the disk, PP and TO bearing were in very good condition but with a total lack of lubrication. No lube and almost frozen disk to tranny shaft spline and no lube at the TO bearing sliding hub in the bell housing. For the latter I drilled a 45 deg. hole from underneath thru and into the sliding hub‘s guide bore and drove in a press fit zerk fitting, for next time. Reassembled with all the original parts and these two areas greased. Problem solved, but still near the end of clutch adjustment range. A design tolerance problem, IMO.