Hi, I need a little help. I just bought a 1980 Vette and the cruise control did not work on the way home. I looked under the hood today and found a vaccum line off that runs to a box on the drivers side fender. There are two cables that lood like speedometer cables leaving the rear of it. One is going thru the firewall, maybe to thespeedoand the other looks like it might be going to the trans. There is a vaccum line coming out of the front bottom with a T. One side of the T is routed back to the box and the other line is the loose one. I can't seem to fine a place for it to hook up. This may not even have anything to do with the cruise, but it looks like it might. I didn't know that the cruise worked off vaccum, and maybe it doesn't. Help!! Harleyboy

 

I believe that in 1980 the cruise control worked off of a vaccuum line. I had the same problem on my 94. One of my vaccuum lines came off cause of the bumpy roads and I also think the line is a little dry rotted. If you cant find a connection for it, I have no clue what to tell you, but when I looked at mine, I immediately saw the connection that the vaccuum line went to. Ill look more into it for you and see if i can figure anything out. Sorry [&o]

Matt

 

The "box" you are referring to is probably the vacuum reservoir. The older GM cars use the speedometer cable like you describe which is split at the transducer. Does your speedo work? If it does, then the transducer is ok. The main problem the older systems had was the transducer locking up and messing up the cable end coming from transmission. The open end of the vacuum line is supposed to go to manifold vacuum with a one way vacuum check valve and teed off to the vacuum reservoir.If everything is hooked up correctly and your switch is operating correctly, you might have a bad transducer anyway.[8D]

 

Thanks Matt and Mech, My speedo works fine. I'll look tomorrow around the manifold and see if I can find where it goes. It seems pretty simple that I should be able to stretch out the line and see what is close to it, but today I didn't see anyplace that it would go.