Bush Hog Slip Clutch Adjustment

wolc123 · Apr 23, 2022

I bought a new Bush Hog, Medium-duty, 5 ft near the end of the season last year. I did not service the clutch at all last year (probably only put about 20 hours on it) but it seemed to be too tight. One time, I backed into a big stump that I did not see and it stalled my 43 hp tractor.

This morning, I serviced the clutch per a video I saw on youtube. I backed all (8) nuts out 2 turns. It would not slip at all when I engaged it. I backed the nuts out another turn and it still would not slip when engaged. At that point, I left them loose and ran the tractor back to a hedgerow that had lots of 2-3" brush. After chopping up about 100 yards of that, it finally loosened up and spun free.
I tightened the nuts back up two turns (leaving them all one turn looser than they were when it was new).

Hopefully, it will slip the next time I hit an unmovable object. The point of the clutch its to protect the driveline and gearbox of the tractor and Bush Hog. Prior to this one, I had a 6 ft Rhino Light duty which used shear pins. That light duty 6 footer took less power to operate than the 5 ft medium duty Bush Hog. I averaged about (6) pins (1/2" gd 5 bolt) sheared per season, and they were a real pain to replace. The gearbox on it lasted 15 seasons. Hopefully, the one on the new Bush Hog will go longer than that if I keep up on the clutch maintenance.

wirlybird · Apr 24, 2022

Slip clutch adjustment will depend on the type of slip clutch.
If it is the type with springs on the bolts then in general you would tighten each bolt/nut until you can't turn the spring by hand then go another 1 1/2 turns.
I have another type which is adjusted by a measurement between two plates.

What you experienced is what can happen to a slip clutch when sitting over time or simply being way too tight. It freezes up. Sometimes it requires disassembly and cleaning of the components.
Your brush hog manual may have directions for setting the slip clutch for your unit.

As a side note, shear bolts are usually grade 2.

Lineman North Florida · Apr 24, 2022

I have seen people not do maintenance yearly and seemed to never have a problem but I have also seen people tear up all sorts of things, yolks, U joints, as well as whole PTO shaft demolition, so to me the 30 minutes it takes to do it yearly is time well spent.

Hay Dude · Apr 24, 2022

Constant use is your best friend to keep slip clutches working properly.

nybirdman · Apr 24, 2022

I do mine every spring;you did it correctly.

CobyRupert · Apr 24, 2022

Last year, the bolts may of been adjusted correctly, but it may have been “too tight” because clutch was rusted from sitting in dealers lot for who knows how long.
But, I guess if it mows and doesn’t slip it’s “tight enough” and provides the most protection. But how to know if it’s slipping unnoticeably and slowly burning up clutch?

wirlybird · Apr 24, 2022

CobyRupert said:
Last year, the bolts may of been adjusted correctly, but it may have been “too tight” because clutch was rusted from sitting in dealers lot for who knows how long.
But, I guess if it mows and doesn’t slip it’s “tight enough” and provides the most protection. But how to know if it’s slipping unnoticeably and slowly burning up clutch?

What I do is put a white paint mark across the disks to indicate movement. If you hit some stuff and feel it should have slipped you can check it.

wolc123 · May 13, 2022

I put my bush hog to use yesterday, for the first time since freeing up the slip clutch this spring, and it seems like it is now working just as it should. I chopped up about 3 acres of standing corn stalks with it and mowed a few lanes.

A few times, when I bottomed out the blades, I could see and hear them stop turning. I don’t think that clutch had ever slipped from when it was new until I loosened it up (with considerably difficulty) this spring. Prior to that, the 43 hp power train on my tractor was the “slip clutch”.

I am glad I bought the “derated” 43 hp JD model 4120 rather than the maxed-out model 4720 or I may have done some serious damage to my tractor or the bush-hog’s gear box.