Need help please

If it's a dd15 they have strong jakes at 1500to1600 rpm the fact cruise doesn't work probably means a sensor or wiring has a issue .. Jakes are quiet but hold as good as a isx .. The dt12 auto has a Eco roll feature basically it kicks it to neutral to free roll... Either something's wrong or not set right I've never driven the auto version

 

Manauly downshift and use manaul engine fan if you have that switch .. Have you played with 3 postioned switch to see if it's on high .. Mine had on/off switch on steering wheel and 3 position switch on dash .. Not sure how 2015 is set up

 

I pulled rough cut lumber out of Castlegar, BC years ago with no Jake Brake. If I remember right I had to stay down around 15 MPH to keep from smoking the brakes. 9 mile hill with a stop sign at the bottom,lol.
Turning the engine fan on and keeping the RPM up and your speed down will help quite a bit. Be careful, and if you think your brakes are getting hot don't procrastinate, find a wide shoulder and stop while you still can and check them out!

 

As stated above, manually downshifting is probably the only thing you can do other than getting the jake fixed. Of course you don't want to over-rev your engine either. When you get to a mountain, notice what the speed limit is for that mountain then put the truck in the gear that will most closely hold the truck to that speed or below with the least amount of braking. Back in the day there was no such thing as jakes but those mountains were still there so it can be done. Id get it fixed as soon as you can. Good Luck.

 

Kind of off topic here but dang that is a nice truck in your signature T_Trucker! That truck would be sweet to have.

 

I've been over all those mountains pulling 80,000lbs with no Jakes before, and you definitely don't want to be going over 30mph to start on any of them, and may want to go as low as 10 on the steeper grades. Run your engine fan, keep rpms high, and use staggered braking. When you get up to 40mph, use medium pedal pressure to get back under 35mph, then stay off the brake until you're up to 40 again. Use lower speeds for bigger hills, actually get out and look at your brakes at the brake check points, and make sure your flashers are on so CR England doesn't come roaring up your back door at 70mph trying to make some time.