AW4 Torque Conv.

Noticed the motor sounding strange, a little louder and seemed to miss the shift to OD. Then the trans temp rising. Hmmm. Manually select TC lock and it locks, rpm decrease, temps decrease.

Couple days of observation shows that sometimes it runs normally. Then sometimes it wont lock (even on highway, low load) so I have to manually lock it. Seems random.

89 AW4, 265,000 mi, fluid looks good.

What would cause it to not lock occasionally, yet it will lock when overridden?

Dirty or out of adjustment brake switch. The white one way up on top of the brake peddle, not the lower one. There is one lower for brake lights and one higher for the TC lock up.

The switch can be cleaned, taken apart, and reused and adjusted. Look for older threads with pictures in this OEM forum. Search "Torque converter lock up switch"