I've ran out of ideas, haven't had the time to go under the car so I would like to know your opinion. I was riding my '67 Mustang, until gears suddenly felt stiff to engage, afterwards I realized the clutch wasn't engaging. I went under the hood and tightened the adjustment rod and then the clutch became all right. Although, 20 miles ahead it did the same thing all over again, and now I have reached the max of my adjustment rod, so I am not sure what the problem is. The cable has less than 2 years and seems in a great shape. Do you guys have any idea what can be behind this ?