I'm reasonably sure it won't work on yours/ours because of the way the torque converter locks/unlocks, the engine retards, but without it being in charge of the torque converter it will just slip so engine won't provide any braking effect. I think there are a couple out there that have tried with limited to no success.
How heavy are you hauling where you think you need engine braking assist.
Pulling a Komatsu D21-5 that weights est. 8,000 to 10,000 lbs. I would like a little more breaking down hill. I will try to up grade trailer brakes. Truck pulls load good with no problem. ABS brakes seems stopping distance is extend.
I haul 18K of backhoe & trailer every now and again, so I know your "issues", if trailer brakes give it up; it could be a "interesting" stopping problem. I recently upgraded to disks for rear, I don't know if they make em for 3500s.
Prior to that something that did help was stainless brake lines, drilled rotors up front, performance pads, and keeping the rears fully adjusted out to where they give a slight drag when wheels are rotated. Also what brake controller are you using, I like the Prodigy, with ability to set brake "boost" so that trailer is doing most of the stopping work.
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