12V71 Kenworth pulling Satus pass part 1

12V71 Detroit pulling Satus Pass in Washington, 3107 FT. 1973 Kenworth W-923. Good sound. The first few minutes not much pulling, then we get into the hills. Light load going up and down hills with Jake. The left window is down about two inches, I lowered the right door window about two inches after cresting the hill.