Slipping PTO Clutch on MF 20

   / Slipping PTO Clutch on MF 20 #1  

ScipioUSA

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Jul 29, 2019
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95
Tractor
MF 20 Industrial, Ghosts of Farmalls Past
Hello all.

I have a problem going on with my Massey Ferguson 20 Industrial with the 6 Speed shuttle transmission. It has a two stage clutch, no multi power or independent PTO.

Tried using a bush hog the other week, and noticed the PTO was slowing down (mower noise changed pitch), but my RPMs were not. Ut oh.

Took off the inspection plate and found what you see below. Any thoughts on if this is normal looking, or is something definitely out of sorts? Things are close to spec between the bolt head and the plate, but not sure that the plate should have that much gap.

Would appreciate some input, since I dont know for sure what I am looking at.
 

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   / Slipping PTO Clutch on MF 20 #2  
Mechanically. it all looks right to me. The exception would be the fresh oil drops I see working down around the cross shaft. That indicated some leaks above, possibly getting onto the clutch plate surfaces. Good reason for slippage under load. No adjustment for that.
 
   / Slipping PTO Clutch on MF 20
  • Thread Starter
#3  
Thanks Harry.

I also thought it looked pretty oily in there, and after running the PTO for a few minutes there are some drips from the rear weep hole on the underside. So probably a leaky shaft seal...

Appreciate knowing the plates and things seem to look as they should.
 
   / Slipping PTO Clutch on MF 20 #4  
"Looking as they should" isn't much comfort if you need to split the tractor for a new clutch as well as leak repairs. But yes, other than the oil, it does look like it would all function.
 
   / Slipping PTO Clutch on MF 20
  • Thread Starter
#5  
"Looking as they should" isn't much comfort if you need to split the tractor for a new clutch as well as leak repairs. But yes, other than the oil, it does look like it would all function.
You are right about that. I guess I should say that it makes me feel better that I couldnt see anything wrong, other than oil, and you are helping confirm that.

I did notice that the bolts at the end of the clutch fingers look as if they are not completely parallel to the throw out bearing. Im guessing they move based on wear, and thats why they have a rounded head...

Do you happen to know if you can replace the transmission side input seal from the clutch side? Or does it need to be done from the center section?
 
   / Slipping PTO Clutch on MF 20 #6  
The three contact points on the release levers SHOULD be in unison as they touch the bearing face. The angle at which you're viewing them may affect your perception of distance, but if the bolt adjustment is off by much you will most likely notice it in the clutch action. The rounded head rolls against the bearing face as the action takes place. They don't usually wear much in use.

I'm pretty sure the seals are accessed from the clutch side of the transmission. I've never done it on a shuttle transmission. It's pretty simple on the eight speed, and a bit more complex on the standard six speed.
 
   / Slipping PTO Clutch on MF 20 #7  
What you describe sounds like the pto disc is slipping. I had the same problem with my Massey 20C and was able to adjust the clutch to get more life out of it. Below is a guide that Big Dean made that describes the adjustment process.
1696896908185.png
 
   / Slipping PTO Clutch on MF 20
  • Thread Starter
#8  
What you describe sounds like the pto disc is slipping. I had the same problem with my Massey 20C and was able to adjust the clutch to get more life out of it. Below is a guide that Big Dean made that describes the adjustment process.
View attachment 826169
Thanks for that image. And yes, it certainly seems that the PTO disc is slipping. But one question on this. It says to make the adjustment if there is an issue with "release". I'm guessing that means when you have your foot all the way down the PTO disc is still engaged enough it's hard to engage the PTO.

It seems like my problem is the opposite. Am I just thinking about it wrong? I'm happy to try and take a few thousands out of the gap if it would save me a split.. I know It won't fix an oil leak, but at least could buy me a little time.
 
   / Slipping PTO Clutch on MF 20
  • Thread Starter
#9  
Minor update.

So I checked my service manual. Looks like to remove the input shaft, I have to pull the PTO shaft out the back of the transmission, AND remove the forward reverse shuttle fork. Makes trying to replace those input shaft seals even more fun than just a split for the clutch.

Im going to try to adjust the clutch per Big Dean's instructions (side note: I really wish I had his second CD with the Industrial specific info on it....) and see if it helps.

Any idea if trying to spray things down in there with some brake cleaner might be helpful? Or should I say, will spraying brake cleaner in there damage anything? Ill do my best to keep it off the throwout bearing so it doesnt get dry, but I dont think there are any other seals that could get harmed, right? If I can clean some oil off of the surfaces and the friction material, maybe it will work for me, or at least let me troubleshoot things better.

I never thought that a rear main seal might look like an "easy" fix compared to the alternative...
 
   / Slipping PTO Clutch on MF 20
  • Thread Starter
#10  
Figured I would post an update. Adjusted the clutch through the inspection cover down to around .060. I like the action much better, but it didnt matter as far as the use of the PTO was concerned.

Sprayed some brake cleaner around in there to try and clean things up, including blocking the clutch pedal and spraying in by the clutch disc. Lots of stuff came out, but mostly looks like it stripped the paint off of the clutch springs. Tried it out with the bush hog again and no better results, except now I could smell a little burning clutch whereas before I could not.

There is a minor amount of oil leaking from the front weep hole, but lots more from the input shaft side, so looks like that is my culprit. Ill need to see if I can get the tools together to attempt a split, or do I want to pay my way out of this one. Old iron gets expensive fast if you cannot fix it yourself....
 
 
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