Now the engine won't start. The starter cranks the motor over strongly, and I can hear the fuel pump engaging strongly, too.

I had just filled up the tank, and it wasn't a mile and a half down the road that all of this happened. Is there an engine condition that can cause this, and this is just coincidental with the trans issues?

I appreciate everyone's help. I'm out of my depth here, and this truck has been great to me. The truck not starting has only ever happened when my battery was going out, or an ignition switch was bad. This is definitely not normal for this truck.