Engine Brake - 2014 Cascadia With Detroit Engine

Question for experienced drivers: I've been driving my 2014 Cascadia for almost a year. I use the engine brake whenever roads are dry. I've experienced something a few times that I've been unable to figure out.

The engine brake works well, and I depend on it regularly. However, the times I've been on a descent of 7% or more, it doesn't work. And that's when I need it the most!

I can feel and hear when it kicks in, but for some reason going down a steep descent it doesn't seem to engage. Everywhere else, no problem. When I get to the bottom of the hill/mountain and I let my speed pick up, I can touch the brakes and engage the engine brake. But when I'm in 7th gear (for example), trying to keep my speed near 25 mph, no engine brake.

I've read the manual to see if I'm doing something wrong, but I didn't find anything helpful there.

Any ideas? I'd appreciate any feedback.

Try 6th. If you're in 7th and trying to maintain 25mph, the rpm is way too low for the Jake to have any effect. Don't be afraid if it's turning 15-1600 on the tach, the engine brake works better at higher rpm and you won't hurt that motor.

I have found the best engine braking on the dd15 at 1700+ rpm. I believe that engine can go to 2100 rpms with no problems maybe even higher been a long time sense I have driven a truck with the dd15.

Totally agree. The higher the RPMs, the more effective the Jake will be. Make it scream!

On my trainer's 17 cascadia automatic, we regularly hit 2200 rpm with the jakes. Whether that was proper or not, I don't know lol. But he was ok with it and the braking effect was impressive.

Do you have a high and low on the Jake...I accidentally hit it into low and had a similar experience.

The other issue could be the cruise control. My trainers truck had Jakes that didn't kick in until 10mph over the cruise setting....so if you are setting cruise and riding down, the Jakes wouldn't set until 35mph.

Take the cruise off if yiubare using it and set it to high if it isn't.

True, the higher RPM the greater effect of the engine brake, but I wouldn't push it beyond 1800. 2200 is just asking for damage. Drive better so you don't have to make it scream.

I would head to the mechanic and have him take a look. Could be a wiring issue, I've had that happen when I drove that exact same truck with same specs as yours.

I appreciate the feedback. I had another chance to try this out today. 7 degree descent, 3 miles. Once again, the engine brake works everywhere else, but provided no stopping action on the descent. I made sure cruise control was off, engine brake was on, and set to high (40k load). I let it rev up to 1800 (per the manual) with no result. It would easily have keep revving up to 2000 and beyond.

I'm going to take it into the shop.

Good call!

Took it to the shop. The mechanic checked it out, but found no problems. He told me he's heard the same thing from about 50 drivers. It appears the Cascadia just had weak engine braking. Not that big of a deal I guess unless you're driving the Rockies. If I were, I suppose I would be crawling downhill in 6th gear. Or 5th. :-/