Ben,
Engine brakes (Jake brakes) stop working 8 out of 10 times because of electrical connection issues, the other 2 times it's mechanical and expensive to fix.
Jon knows the Prevost scheme and will send you in the right direction.
Ref your turbo issue, first question I have is how do you know it's the turbo ?? Sounds like it could be several things (turbo included). Would like to know the boost pressure readings and pryo readings when the problem occurs.
The braking question... I guess that old saying about down in the same gear as you climb up in is "ok" as a guideline only. My experience is the go ups are never the same as the go downs. But having said that you almost can't start too slow at the top. Easy to let it pickup speed as you get to the bottom, not so easy to slow down if you let it get away from you. Flip on the flashers and don't worry about anybody else until you are down the grade safely. They'll go around.
I'm one of those that disagree with the stab the brakes method....mostly because in the "old" days the CHP used to say slow steady pressure...now they have changed their minds. I will say it's a multi-faceted relationship between weight, grade, speed and applied braking pressure. Point in reference, I could go north on I-5 in California and descend the "grapevine" at 80K, no Jake, hold speed at 25-27 MPH and hold a steady 5-7 pounds of applied brake. Never smoked the brakes and never played in the sandbox.
If you start stabbing the brakes too much you will build heat, feed nice fresh Oxygen into those hot brakes. Get enough and you'll have fire.


I just checked Ashland weather, light rain down in Ashland, so I expect the pass to be snowing. You'll find that all across until you make Redding. If your in California and can make Redding your mountains are over. If your past Ashland maybe stop in Weed and spend the night. Tackle the "canyon" (down through Shasta) tomorrow in the daylight.

Michael
Flame proof suit on....