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73-87 Chevy _ GMC Trucks => Interior & Equipment => Topic started by: GrumpyRetiredGuy on May 21, 2026, 12:10:29 pm

Title: Cruise control speeds up
Post by: GrumpyRetiredGuy on May 21, 2026, 12:10:29 pm

1987 R10 350/700R4

After replacing the control arm on the steering column I was happy to see the cruise control works on this old girl. The issue is it  will not maintain a steady speed on a flat straight road. The speed creeps up as I'm driving. Any suggestions on what to check would be great. Thanks in advance and happy wrenching.

Title: Re: Cruise control speeds up
Post by: bd on May 21, 2026, 02:31:54 pm

Welcome to the Forum.  I suspect that either the servo vacuum valve solenoid is sticking and bleeding vacuum to the servo diaphragm, or the servo vent valve solenoid is sticking, or the module is failing.  See the Custom Cruise III (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Training/1984%20CRUISE%20III_opt.pdf) manual for system operation.