Erratic Shifting in Cruise Control (1 Viewer)

[thebovees]

Took my '94 80 out for a 50 mile test drive after working on the instrument panel, LED lights, Apparently found problems in Cruise Control. On level highway all appeared OK. As the grade steepened I noticed that the speed would randomly, suddenly drop 2-3 MPH and recover in a second or two. This bounce would come fairly often. On steeper grades, suddenly the transmission seemed to shift randomly between 2nd and 3rd multiple times. I just verified what it was doing and quickly shut of the cruise which stopped the shifting.
The next morning, came to a stop sign and as I started out the transmission had not shifted down to first so I had to manually do it and the rest of the short trip was uneventful.

 

[Malleus]

This is normal behavior. The cruise control is supposed to suspend the setpoint if the speed varies 2-3 mph outside of the setpoint and accel/decel until the speed is within the set range. O/D is also affected by this control logic. The whole story is in the transmission section of the FSM.