I have an 80C series No, 12 grader with an oil clutch, and my master clutch brake isn't stopping the clutch. Consequently I can't get the transmission in gear without a lot of grinding. The Serviceman's Reference Manual that I have (FEO30124-03) references the dry master clutch and not an oil clutch.  My Operation & Maintenance Instructions explains how to adjust an oil clutch but doesn't explain the transmission brake  My parts manual references a "Transmission Brake" which my grader has but I can't find our how to adjust the transmission brake.  Can someone explain how the transmission brake is adjusted.
Thank you.
 

There really isn't any adjustment. The brake is a spring loaded affair that is loaded by clutch pedal position. Operation would depend on the springs and condition of the friction disc and plates. Same brake arrangement for both dry and oil clutch.

What I can gather by looking at the grader and the parts diagrams; When the transmission is in neutral or in gear and the master clutch engaged (pedal not depressed), the transmission drum should be spinning.  When the master clutch pedal is depressed, the master clutch disengages and a control lever forces the transmission brake shoes against the transmission drum and the drum stops spinning.  Because the transmission shaft is connected to the transmission brake drum, when the transmission drum stops spinning then the transmission shaft stops spinning and the gears can be shifted without grinding.
Having said all that; My transmission drum does not spin when master clutch is engaged (pedal not depressed).
What am I missing here?
 

I think your confusing the transmission brake (at main clutch) with the hand brake in the transmission drum.
In neutral or with main clutch disengaged the transmission drum is not going to spin unless the grader happens to be rolling.

DeltaKJ as OM said above, you are confusing the parking brake with your clutch brake. The brake you pictured is operated by the lever in the cab for parking. The clutch brake is inside the bellhousing. That brake drum you are referencing only turns when the machine is moving as it is on the opposite end of the main transmission shaft that has the differential pinion on the other end.

You guys are right… I was confused.  I am familiar with crawler tractors and pushing the master clutch lever forward to activate the clutch brake.  Apparently the grader uses a similar clutch brake albeit activated with a pedal.  The parts book references the parking drake drum as a “Transmission Brake” and that started my confusion.
The grader was shifting fine but now will not disengage the clutch and/or activate the clutch brake.  I’ll pull the adjustment plate on the left side and investigate.
Thanks for straightening me out 😁.
 

🤐 I'm trying not to sat anything