95 Silverado, 271000 miles.
Recently it started shifting into 2nd at 30mph from a previous 22 mph and into 3rd at 55mph. I have not done anything to the engine or transmission. Can anyone tell me why the shift points have changed, and how do I change them back? Last week I changed the fluid and filter, but that didn't change anything.

This is a 4 speed automatic, and it doesn't have the governor bubble on the exterior of the case...ideas?

-greg-