It don't have a jake brake. It probably has some sort of exhaust brake though. Banks speed brake or using the stock turbo vanes through tunning.


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An actual Jacobs Brake on a Dmax...no. :rof

A tissue isn't always a Kleenex, as well as an exhaust brake isn't always a Jake Brake.

With available aftermarket tuning, it could be utilizing a Turbo Brake to slow speed (like most of us with EFILive). If that is what the seller has, with T/H engaged and utilizing the Tap-Shift with the Ally 6-speed, you should be able to tell with downshift actions coming off from highway speeds.

 

Jacobs does make an exhaust brake as well, but not for a Duramax. It could have an exhaust brake in the tuning or an aftermarket one that uses the turbo veins as well. It could also have a butterfly valve installed in the exhaust stream. Look in the cab for a switch or knob that might say Pac, BD, Banks, US Gear, etc. You can also follow the exhaust from the turbo back to the muffler and look for a butterfly valve with an air/vacuum cylinder or electric solenoid in the exhaust pipe.

 

Its also possible the truck is the first truck this gentleman has owned with a modern automatic that actually holds back and downshifts to hold speed on hill decent etc.

Ive heard a couple old timers refer to the Tow/Haul feature as an exhaust brake, engine brake etc.

 

Jake brake on a Duramax would be awesome though if it was possible LOL