I've got a 2003 Chevy Silverado 2500HD, it's got about 38,000 miles on it and this morning, on my drive into work, the transmission started to slip in 3rd and 4th gears. I had to drive about 1-2 miles past the point of the trans light coming on in my cluster. I parked the vehicle and checked the trans fluid, it was dark, but the fluid didn't smell burned. I was unable to check the fluid level.

All this happened after about 35 min of driving at highway speeds then turning off onto a surface street. The ambient temperature outside was about 0 deg F. I had my grille covers on.

Any ideas what kind of failure this might be? Have very many other people reported failures at about 38,000 miles?

What light came on?