IH 300U PTO issues

I have IH 300U and when I engage the PTO it works, but when I hook up a brush hog and engage it, it will turn the blades intill I go to use it, and then it Peters out and acts like something is slipping.

That tractor has the independent live PTO and it has a clutch that could be going bad or out of adjustment.

It is a band operated PTO. The bands are adjusted as follows: Move the lever exactly half way
between the locked on position and locked off position (little flipper catch on lever. Use bungies
or ratchet straps to hold it centered. Measure this position.
Take off the little dome metal cover from the adjust screws.
Loosen the jamb nut, and tighten the front (away from you) screw until it is just a bit tighter
than the point at which it begins to feel tighter as it is screwed in (maybe a eighth turn) then
back it off until the PTO shaft will turn with least drag (about 3/4 turn out) and tighten the
lock nut while holding the adjuster.
Do the same for the closer adjuster.
If the screws go into the jamb nuts and get flush with the top surface of the nut, the bands are
probably worn out, and may be operational for a while, but plan on a rebuild.
Now (tractor off) push the the lever down toward the brake footplate. As it goes down, it should
get harder to push when it is about 4" (or so) away from fully OFF. and be noticeably harder to
push for the last inch, but not real hard. (this is the brake band tightening on the drum in the
PTO unit.
Then pull it up and do the same feel.
The ON position should feel the same way.
The shaft should turn pretty free when the lever is half way, and not at all when in either ON, or
OFF. (tractor shut off)
If it slips now, it needs a rebuild. Jim