My book shows 1976 is correct. I can't remember if those have the dry disk brakes of the old stop master actuated drum type brakes. The dry disks look just like the front brakes on a passenger car, just bigger. The stop master systems used a single cylinder that pushed a wedge out to apply the brakes. These systems are adjusted with a star wheel on the end of the cylinder. I know the B model 950s had the disks, I just don't remember if the A models had them also.
Both brake types are operated hydraulically with two master cylinders, one for each axle, that Cat called power boosters. The two power boosters are located behind the cab and have air cans attached to the backs of them. There are stroke indicating rods that extend into the air cylinders. The rods actuate an electrical switch that turns on a light on the dash panel when the piston in the air cylinder moves too far. As I recall each power booster has it's own separate reservoir. There should be a decal next to the reservoir that states what kind of fluid to use. I think most I've worked on used hydraulic oil but I have seen systems that used brake fluid as well. Someone here may know. A service manual is an absolute must to have, especially if you have limited experience with these machines.
Good Luck!
