Potential mechanical issue...

.....

 

I'm totally confused about this whole thread. I'll just say to me, sounds like something "ain't right" in that engine. The word "shutter" keeps coming up and now I think I'm hearing this is not when the truck is decelerating up grades but when coasting and engine braking? That's not normal under any circumstances.

Drivers can control jakes any number of ways. Neither is wrong or potentially damaging.

 

There are a number of conditions that control the jakes.

-Jake switch on.
-Clutch position switch must sense clutch is released.
-Engine RPM (should deactivate below a preset RPM).
-Zero accelerator pedal input.
-If the jake is set to activate while on cruise, it should read ground speed as well.

There should be no reason for the jake to activate while the accelerator pedal is pushed. Not unless your T680 has a mechanical Cummins under the hood lol.

 

I agree but if you are bouncing around in the cab, don't know how to hold your foot on the accelerator steady, the signal to the ecm from the accelerator will be all over the place and the ecm will turn on the engine brake and fuel the cylinder within a second.

Where I used to work, we had a driver who would do this on his way down to Ohio, he try to coast down the rouge river bridge (which has a steep decline) hold the accelerator just enough to allow it to pick up speed without kicking in the EB with the cruise on, if he was in one lane it would be a little bouncy and he would do this exact thing, his foot would move right on the edge of the accelerator pedal sensor to send the signal to the ecm to fuel the engine, then the engine would buck as if something is wrong.