96 379 Cruise Control Gremlin

I had a bad sensor on output shaft on transmission cause that problem.

 

Speedo sensor would be my 1st suggestion. Some rigs have dual outputs.
When I was troubleshooting this, I simply swapped connections at the speedo sensor output since the speedo worked.
That wasn't it...


This wouldn't happen to be a Detroit Engine would it?
(asking since I don't know if 379s ever came with DD or not...)

 

Check the brake lite switch for the cruise if you take off the steering column panel it will be on the right side of the coloumn support looks like the brake lite switch it has an aluminum body bolted to the main dash structure with one 1/4 air line running to it if the switch goes out cruise will be in-op also if the truck is new to you you might want to hook a scan tool up to it and verify the settings could be some one set it up for the pto if it has one

 

Loose yoke on the output shaft?

 

I own a 95 379. Just replaced that switch on mine. Bit of a pain. The swicch is located on the channel iron that runs across the cab bahind the dash. Looks like a standard switch except for the fact it has a 1/4" nipple.All thumbs here got it out and in with some amount of patients.Tight spot.You will need a sender socket to r&i. About 5 bucks at Napa. You might also look for the Cruise switch on the clutch linkage. It is found right under the drivers door. Another tight squeese, but did them both out on the drive.