Cruise Control Surging

[helievacpilot]

96 F350. Did some searching, but still have questions. My c.c. surges 1-4 mph going down the road empty. When loaded, it gets worse. I had the diff cover off this summer, but at the time did not look at the tone ring. The speedo surges as well. Would the sensor on the diff. cause this or should I look somewhere else?
Thanks - Bill

[madpogue]

So the speedo "surging" means it's not accurately reporting the speed? Then yes, it would cause cruise issues. It would also cause shifting issues if it's an automatic. Sensor, tone ring, contaminated fluid, wiring to the sensor are all on the suspect list.

[helievacpilot]

Originally Posted by madpogue

So the speedo "surging" means it's not accurately reporting the speed? Then yes, it would cause cruise issues. It would also cause shifting issues if it's an automatic. Sensor, tone ring, contaminated fluid, wiring to the sensor are all on the suspect list.

Yea, it has kicked off when it's surging bad. I'm going to assume for now that the tone ring is ok since I didn't pull any metal out of the diff. New fluid. Guess it's the sensor or the wiring. Does the signal go to the computer first and that's why the speedo is surging as well?
Thanks -Bill

[351fifty]

You could pull the sensor and try cleaning it as well

[helievacpilot]

Thanks, that'll be my first thing to try. Don't remember if I pulled it when I changed the fluid. Getting back to the speedo surging as well. Does it get a signal straight from the sensor or the computer?
Thanks - Bill

[madpogue]

The signal goes to the PSOM - programmable speedometer/odometer module - in the dash, which in turn feeds the speedo pointer and then also feeds the PCM. The PCM runs the cruise. So any issue with the sensor, tone ring, wiring, etc. will affect both.

[helievacpilot]

Thanks, when it warms up a bit, I'll clean the connector and see what happens.
- Bill