I just got done replacing the 4.2l engine in this truck and during the test ride, I noticed that the brake lights stay on. There are three bulbs in each taillight....The top and bottom bulbs are dual element bulbs and the reverse light bulb is in the middle. My question is why do the bottom bulbs have two elements? They do not flash with the blinkers or come on with the brake lights????? THANKS!!!

 

I think you will find it is to increase the brightness, and get more money out of your pocket because one bulb wasn't blowing fast enough for them. But seriously my guess is brightness unless someone has mistakenly replaced with what they had and not with original parts.