98 GMC Sierra cruise control

I have a 1998 GMC Sierra 4x4 Z71 that I purchased about a year ago. It has 287k on the clock, but is in incredible condition. Runs like a top, looks like a new truck and is clean as a whistle. However,
the cruise control has recently begun acting up. It works sometimes, but not very well. It will engage, but not hold speed, but then if I'm holding down the gas pedal, it will sometimes decide to work for a short period of time before slowing down or not working. I have a Haynes manual for it, but that's totally useless. All it shows is a cruise control wiring diagram and the fuse location (#6). I checked the cables and the connectors to the controller, and all seems to be in order.
I did recently replace the steering column turn signal switch, as it had a bad washer portion, but the cruise problem was prior to that and the new switch is working fine.
Any ideas on where or how to start looking for an answer before I have to take it into the dealer and get fleeced, or just live without a CC?
Thanks
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When your cruise control fails to work, put your toe UNDER the brake pedal and pull it up. Try to reengage the cruise control. If it will reengage then, there is an adjustment that can be done on the switch. KenG the above was posted to another poster with the same problem as yours about a week ago in the chevy truck group by KenG. the guy with the problem just tonight thanked KenG for the fix. so i'm just passing it along .
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says...

Tried that this morning, but no joy. The cruise eventually engaged, but wouldn't hold speed. Brake pedal is tight up against the rear stop (no play upwards).
Any other suggestions?
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I had this issue with my '94 Suburban K1500 and the cruise module was flaky. It's an electromechanical part that reels in and retracts a small belt and the gears and rollers eventually wear out on some. On others it's the electronic part of the module. The nylon gears wore out and broke on mine. Wouldn't hold speed. On a '98 it's not a cheap part new, and from a jobber it's $390. I'd suggest a wrecker.At least that what I did. It's an easy replacement to do yourself and cost $100.
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