heater and 2nd gear ??

have a 96 with the aw4 tranny and when i turn on the heat the tranny shifts it's self into 2nd gear ? turn the heat off it shift's to 4th gear ?? any thoughts on that problem ?????:banghead:

That's definitely odd. For second gear both shift solenoids are energized, versus both off for forth gear. Seems like a bad ground would cause solenoids to drop out rather than suddenly engage. Perhaps there still is a bad ground somewhere and its affecting the TPS signal?