Importance of spring on bush hog slip clutch?

[SPYDERLK]

Got me a JD bush hog with slip clutch from a neighbour to deal with my willow problem in my pastures. I guess I was stupid. I greased anything I could, changed gear oil, ignored the clutch for some reason and went out brush cutting. Worked great until I hit a rock, and the clang-clang-bang reminded me to check the slip clutch!
Luckily the rock was very shallow, the tractor old and tough, and no damage was done to anything.

The clutch was seized for decades. I freed it up with hammer, screwdriver and copious ATF, but now it is loose and slips too easily - the funny disc spring that goes behind the clutch stack had shattered long ago.

Can I just tighten the nut until the clutch grips enough, or should I be looking for another disc spring? Being green the price is sure to be fairly dear for a new one, and the entire stack has to come apart to install it (the driven discs are still seized to the shaft)
I would like to get going ASAP as the conditions are perfect this time of year to cut willows and leave the pasture grasses untouched.

What model JD bushog?

 

[rectifier]

Just ID'd the hog as Model 127 Gyramor. Wow, it is even older than I thought!

Now I'm really impressed that the gearbox looks like it was brand new inside after all those years of smacking rocks.
Got the parts manual PDF and it looks like I need part W10146.

However if anyone knows if the clutch can be readily replaced with a new aftermarket clutch, that would probably be for the best. Especially as the castle nut has so far been very reluctant to turn.
Looking at the exploded view it looks like it is not part of the input shaft, but simply seized onto a keyway very solidly. Changing to a shear pin setup would be an option too I guess but I think everyone agrees that shear pins are a pain in the ***.

 

[LD1]

They make all kinds of clutches with various input and output configurations to match up to your gearbox shaft and PTO shaft. Without knowing what those are, we cannot help.

 

[SPYDERLK]

Just ID'd the hog as Model 127 Gyramor. Wow, it is even older than I thought!

Now I'm really impressed that the gearbox looks like it was brand new inside after all those years of smacking rocks.
Got the parts manual PDF and it looks like I need part W10146.

However if anyone knows if the clutch can be readily replaced with a new aftermarket clutch, that would probably be for the best. Especially as the castle nut has so far been very reluctant to turn.
Looking at the exploded view it looks like it is not part of the input shaft, but simply seized onto a keyway very solidly. Changing to a shear pin setup would be an option too I guess but I think everyone agrees that shear pins are a pain in the ***.

That is a very tuf little mower, made by JD as an answer to the Bush Hog. I have been using one for 50yrs.
,,, At 600lbs it is the most capable rotary cutter youll ever find. The gearbox, shared by both the 5 and 6' models, is rated at 125HP. The cutter is rated for 4" trees. Outfitted with the heavy end knives and driven by our 2010 JD I have cut oaks up to 6" and trash trees of 8" going forward. Its light weight makes it usable even on a Kub B at only 4hp/ft. ...

I am still on the original clutch on mine - always kept real tight. I urge you to fix it with JD clutch parts. You seem to need the disc spring and maybe the 2? friction plates if you cant soak out the oil. Its a better clutch and for the parts itll be cheaper than replacing with a cobbed on aftermarket.

For the castle nut -- cotter pin out? -- Use Kroil, heat, and impact to flex the nut radially. --Then a big pair of channel locks should turn it. Of course an impact gun and socket would be preferable.
,,,larry

 

[rectifier]

8" trees?! Sounds like it will just eat up my willows, they are lucky if they are 1" usually.
The front castle nut where the grease nipple is just spun off by hand due to being nice and greasy. The rear one is the one that is stuck... there is no getting a socket on that guy at the moment.

Since you say socket/impact that implies the clutch will come off without having to remove that rear castle nut. Hard to tell, as everything is siezed like it was one piece. What actually retains the clutch on the input shaft? Can I remove the front castle nut, apply a gear puller and tug it off?

 

[SPYDERLK]

I just took alook and my memory was turned around. -- I was referring to the rear nut thinking it was on the front .

I have never had the clutch apart, only adjusted that rear nut to set spring preload to prevent the clutch slipping in trivial circumstances. ... It looks like removing the front nut would allow you to get the clutch "finger cage" off. A puller should coax it off, but if that rear nut would turn inward it would probably apply the same directional force from the inside to help get the cage off. ... maybe not, but youll finally need the inner nut to adjust preload anyway

To help break the nut free use penetrants for a bit and then flex the nut by putting a reaction mass [like a substantial piece of 1/2" steel stock] against one flat and then use another piece of steel as a punch on the opposite flat. Hit that "punch" with a 3# hammer. Repeat this opposing setup until youve used the punch on each flat. 6 blows, penetrating oil between each. You should now be able to turn it with a big pair of channel locks.

 

[JRobyn]

Just for future reference, any slip clutch should NEVER have any oil/grease/ATF on the clutch plates, any more than you would put them on the clutch plates in your car. And having any on them will have the same effect as having any on the clutch of your car.

- Jay

 

[rectifier]

So there is a roll pin that holds it onto the input shaft hidden under rust and grease. It pulled fairly easily once the pin was removed. And the dealer has the spring for $35 which is not too bad. However if I have to purchase 4 clutch plates at $20 each, that puts the clutch repair at more than I paid for the mower.

That big castle nut though... oh boy.
After using all the techniques I know as well as that interesting idea from SpyderLK, I got it to turn - 1/10 turn at a time, using a torch and 24" pipe wrench hit with a 5lb sledge. I had to rig up some impromptu clamps to hold it down using an old tractor axle and c-clamps (which are all now bent). Once it cools down at all, it seizes right back up.

3 hours later, the nut is only a quarter of the way off and I've had enough hammering, I think I'll go indoors and sit down and work on my swather carb instead!
It's coming to work tomorrow to be heated with a pair of cutting torches, hope it will get it hot enough that I can at least ditch the sledge.

It's getting more and more tempting to drill it for a pair of shear pins, slap the thing back on and purchase an splined slip clutch that mounts on the tractor PTO. But if I can torch that nut off I will soldier on.

JRobyn thanks for the info. I had heard from the old timers that this sort of clutch should be lubricated so that it can slip easily without damage, like a motorcycle clutch. So I felt confident pouring ATF all over to free them up :banghead: It did sound kind of stupid but I guess I'm stupid for believing it! The disks look like they are OK, just oily. If I ever get that stupid nut off, I'll clean them up in brake cleaner and they should grab enough to transmit the 35HP and maybe smoke off any remnant. I don't have big trees to mow, luckily.

 

[Sawyer Rob]

Just split the nut and take it off... Buy a new nut to put back on it...

SR

 

[4570Man]

Fix it. I just helped somebody fix the gearbox in his John deer bush hog. It cost him over $500 and was probably caused by a sized up clutch.