Similar truck, '07 Volvo, similar weight, same geography but different . . or maybe the same . . problem. My cruise control went out (not the pedal switch) somewhere in the wiring and, coincidentally, because the cruise wouldn't work, the jakes wouldn't. Just as I got off the phone with my life insurance agent and was about to roll, the shop beeped in with a question and a suggestion: "Is your cruise switch still on?" Yes. "Turn the switch off!" Switch off, Jakes worked . .

Well I got down to Sacto and drop that load. No problems downhill, started out in 6th and light brake app, slowed down too much, went to 7th and floated down, lightly stabbing them to go from 35 to 30. Got a 16k load going back up to Salem, should be no problem.

I went down the grapevine with no jakes, and that was enough for me. :p
I felt that same knot in my gut, when I skated down an icy Snoqualmie Pass on chains.