Weird Cruise Control Issue

[Mattchu60]

My 87' has had a strange Cruise Control issue for about a year now. Here is the symptom - when using Overdrive and cruise the cruise control will quit for a split second and then come back online. Its annoying because its like lifting off the gas and then punching it within a second (loses 2-3 mph and when it comes back on it goes to like 50-60% throttle to get back to the set speed).

happens in different situations, can happen on a flat road with engine hardly working, or going up a hill where its laboring some.

Here's the strange part - if I leave the trans in Drive (not overdrive) it does not happen ever. This leads to pretty high cruising RPM (almost 3k RPM on the interstate).

One thought I had was a vacuum issue since it does not appear to be an issue in Drive when the engine is running faster? Trans is a 700r4, doesnt seem like its a slipping trans issue to me.

[tucsonjwt]

My 83 C20 with granny 4 speed does the same thing. Sometimes it works fine, and at other times it does the lag and surge thing. It used to work consistently at highway speeds but now that is unreliable.

I think these vacuum controlled cruise control systems are not as good as modern electronic cruise control. If you need cruise I would look into an aftermarket replacement, since parts for these old cruise control systems are hard to find and cost more than a new aftermarket system, if you can even find the parts.

[Mattchu60]

I would be interested in an electric replacement system to replace the vacuum system. Anyone know of a replacement one that would drop into place of the stock one?

[tucsonjwt]

Nope. Just Rostra.

http://www.rostra.com/universal-afte...-by-rostra.php

View the video there.