No OD when engine is cold

[diggerrigger]

I posed this question here about two years ago to no avail. I am selling the car to my nephew and thought I'd ask again before he takes possession.

The automatic transmission on this 1990 SR5, 4AFE will not shift into overdrive when the engine is cold. It shifts after about a mile on the highway. I drive it only about 45mph, 2000rpm till it makes the shift. Once the engine is slightly warm it works fine.

Is this normal?

I live 2 blocks from the highway. My nephew lives in town so it probably won't affect him.

My theory is the EEC is blocking the shift. possibly due to input from one of the many temperature sensors.

[SuperRA]

It's normal. At least my pickup has been that way since new. It's the ECU's way of warming up the engine faster.

[Donald]

My '86 Van was the same. It's normal on some models.