1978 Chevy Suburban Cruise control

A couple of monthes ago I was on the freeway and I turned on the cruise control. When it came time to get off, I hit the brakes to disengage the cruise, which it did, but when I took my foot off the brake pedal the truck accelarated back to 60 miles an hour. The only way to shut it off was to hold the brake and shut the engine off. I then disconnected the three vacuum hoses on the cruise under the hood on the left fender. Is this fixable? If not what do I have to replace. My Speedometer and everything else works normal.

Thanks in advance.[img:f222533f56]http://www.2carpros.com/forum/automotive_pictures/158632_IMG_0436_1.jpg[/img:f222533f56]