As a followup to Dave's and CNKS's excellent advice, it could be a combination of wear and crud. I haven't seen an IH Service Manual for the Super C but the I&T IH-8 manual descibes them and how to work on them better than I can.
What's in there ? Describing just one side here . . . In the center, connected to the rod running in from the pedal, is an actuator that might be described as two roundish, heavy steel plates with an open center. They are held together by springs. Sandwiched between them are three steel balls. The mating faces of these plates are machined with ramps to nest the balls in. When at rest (off the brake pedal) the balls are in the deepest part of the recesses of the ramps, so that the two plates are as close together as they can get. Stepping on the pedal causes the plates to rotate against each other, acting against the springs that hole them togehter, causing the balls to ride up to the shallowest parts of the ramps, which expands the whole actuator mechanism. The bull shaft coming out of the transmission passes through the center of this rig, which is anchored in place and does not rotate with the shaft.
That's part one. Part two is two friction discs, which look and basically are the same as two miniature clutch discs. These fit over splines on the bull shaft, just like a clutch disc over the splines on an input shaft. There is one on either side of the actuator.
I used the comparison to a clutch disc. A clutch engages by allowing the pressure plate to "squeeze" the friction disc between the pressure plate and the flywheel surface when you release the pedal. In the case of your brakes it's sort of the opposite. When you depress the pedal, the actuator expands as the balls are forced up their ramps. As it expands, the inboard side of the actuator forces/squeezes the friction disc on that side against the side of the transmission case, and the outboard side of the actuator forces the outer disc against the cover. It's the friction of the discs, which DO rotate with the shaft, between the two sides of the actuator and the chassis and cover that makes for your braking force.
That took too long to say. It's a simple rig and it's design and function make pretty easy sense and quickly as you dismantle one.
Problems? Rust. If the balls between the two sides of the actuator, or the ramps they ride in are crusted or pitted, the will bind or not operate in and out reliably as they should. If not pitted a simple cleanup will do. If pitted, the balls at least will need replacing, and a good high-speed wire brush clean up of the ramps on the inner faces of the actuator plates.
If the tractor set for a long time, the friction discs could be rusted in place at a spot along the bull shaft that they simply won't slide over the shaft to allow them to press agains the tranny or cover to operate.
On the crud side, and this gets to the seals, Brakes make dust. If you have had oil leaking from the seals onto the bull shaft, brake dust will stick to it, and impede the free movement of all the parts. If you find an accretion of dried, crusty oil inside whn you take one apart, you'll need to deal with the seal where the bull shaft passes through the tranny case as part of your repair.
For that same reason, when everything is clean to your satisfaction and ready to be reassembled, shun the temptation to lube things up inside. Yes, the the friction discs need to move freely over the splines of the shaft, but they don't need lubrication to do it. Do not use any grease or extra oil on them, anywhere, as dust from the use of the brakes will only lead to to the kind of gumming and sticking that could have been the problem in the first place. A light touch of graphite where the balls roll in their ramps is sometimes suggested and probably wouldn't hurt. A little residual oiliness on the shaft wont hurt much either. But no extra wet or sticky (oil, grease, Never-Sieze) should be used.
Once they're cleaned up, put back together and working, about the only thing necessary to keep them working properly will be regular use.
As for wear, the only thing that might require any rebuilding (like what OEM offers) would be if the brakes have been used enough and hard enough that the inner face of the cover, the outer friction surface on the trannny case and/or the actuator plates have been worn down enough so that even a properly functioning actuator with new friction discs cannot expand enough to exert enough force to make the friction necessary to stop the tractor. In that case the rebuild would include shaving down the covers (like planing an engine head ) to reduce the space between the inner face of the cover and the side of the tranny so that the actuators and discs can do their jobs. That said, if wear seems to be the problem, I'd try new actuator plates and discs and see how that worked before I'd have the covers planes down.
Clear as mud, right? Hoping it helps.
Please let us know what you find and how you make out.
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