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Here's the vacuum hose diagram from page 15-25 of the '68 CSM. The system is not that complex, but this diagram isn't very clear, so I put some red labels on it.
Line A (labeled in two places), which is a vacuum hose, connects to a manifold vacuum port on the engine on one end and to the "regulator assembly" at the other end. It is routed around behind the brake vacuum booster. On the regulator, there are two vacuum ports on the side facing away from the engine, and line A is connected to the port closer to the rear of the car (the narrower end of the regulator).
Line B is also a vacuum hose and connects from the other port on the regulator to the vacuum servo.
There are two threaded fittings on the narrow end of the regulator, and speedometer cables attach to both. They're probably there now on your car, so, as long as your speedometer is working, you shouldn't have to touch these.
But just to complete the picture, line C, which is one of the speedometer cables, goes from a fitting on the transmission to the appropriate fitting on the regulator. The two threaded fittings on the regulator are different sizes, so you can't attach the cable to the wrong fitting.
Line D is the other speedometer cable, and it goes from the regulator through a grommet in the firewall to the back of the speedometer head.
How do I know all this? I just got done restoring to working order the cruise control on my '78 Toronado. The diagrams, descriptions, and procedures regarding the cruise control in the '68 and '78 CSMs are remarkably similar.
Wow, Thank you very much, I found a box in the truck with a busted up servo and the linkage and have kept it and it took me a couple of years to get car up and running. After sitting for 25 years in a pole barn! A TRUE BARN FIND! Not just a line of bull. It is a 68 Cutlass Supreme Holiday Coupe Police Interceptor as shown in The 68 Nov, Issue of Motor Trend. It has every option you can think of, but as the article mentions the cruise control is one of the first thing that fails.Thanks again and if I ever figure out how to post a pic I will.
