Since you mentioned brakes on an Oliver......  I'm sure you know the obvious things like checking brake linings, checking mechanical linkages, adjustments to tighten brakes, but I would recommend changing the oil seals on the bull pinions that the brakes are on.  On these older tractors, these seals leak rear end oil and loose braking.  When you tear into them, you can see if they are oily.

RonnieS