Do I have overdrive?
 

My 92 3.9 L D150 Automatic does not have an overdrive button. Can I assume I do not have overdrive, just a 3 speed?

Only the 5 speeds had overdrive If I remember correctly.

The 4 speed auto was an overdrive trans. But my guess would be that without the O/D button, it it 3 speed. The easy way to tell is next time you accelerate, count the number of shifts you hear.