Importance of spring on bush hog slip clutch?

rectifier · May 12, 2015

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.

Coyote machine · May 12, 2015

Fix it.

msmith · May 12, 2015

I would just buy a whole new clutch. You might find one at Tractor Supply

LD1 · May 12, 2015

Get a new one. The copious amount of ATF now soaked into the disk didnt do any favors

pmsmechanic · May 12, 2015

I get a laugh out of people who automatically assume that just because it's green it's expensive. I fix farm machinery for my neighbors for a living. Believe me it doesn't matter what color it is, it's expensive. The only way you are going to know for sure is to phone your dealer and ask what the price is. If it's the spring I'm thinking of it will most likely be very reasonable because John Deere uses that spring in a lot of applications.

ishiboo · May 12, 2015

LD1 said:
Get a new one. The copious amount of ATF now soaked into the disk didnt do any favors

This.

Sysop · May 12, 2015

Go to Tractor Supply, if they don't have the parts to fix that clutch, they also sell new shafts with new clutches pretty cheap. Trying to just tighten it down without the spring will result in having a non-clutching shaft and something WAY more expensive is going to get broken.

rectifier · May 12, 2015

Thanks guys, I'll call the dealer and see if the spring is available for a reasonable price. Unfortunately the mower is so old there is no nameplate, and the remains of the spring are only a couple little shards.

Haven't seen the clutches at our Canadian equivalents to Tractor Supply but maybe I need to look harder. This one looks like it is almost part of the drive shaft for the gearbox, I'm not sure if it can be replaced readily.

I'd always heard that these things needed to be lubricated with plenty of oil to allow them to slip. Is the ATF going to be too slippery? I'm only driving it with 35HP.

Coyote machine · May 12, 2015

Doesn't matter what you're driving it with 35 or 350HP. When the blades spin up to speed and you hit a solid object if the slip clutch doesn't work as designed the torque is transferred upstream to your tractor PTO- BOOM! Remove the shaft AND clutch and match them up. Post pics of the hog and maybe someone here can identify it.
Pay now to fix it properly, or pay later for possibly BIG $$ to fix a broken PTO/differential drive.....
Your call.

rectifier · May 12, 2015

With respect to the low HP I was more referring to erring on the side of too much slip due to excessive oil. Less horsepower should = less chirp when starting it up, right?

As long as the oily old discs grab enough to bring the blade up to speed, I'll be happy. I'd rather run with too much slip, as we have lots of rocks, gopher mounds and funny hummocks out here.

Currently working with the dealer to identify the machine and purchase the spring.