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I observed this change with mine. Leaving my house starts with a 5 mile 5-7% varying, continuous downhill grade. Speed limit 45. With 3.07 without ECO, I hit the pacbrake at 50mph and it downshifted to 5 and slowed the truck to sub 40 pretty easily. I have to turn off the pacbrake otherwise speed willAs I contemplating eco-hubs. My truck is a 2003, 3126 tuned to 330hp with 3.07 gears, weighing 27,600lbs. One of my favorite aspects is the exhaust brake especially going down step 10% grades, narrow 2 lane roads with switch backs every few hundred feet, with no shoulders for miles. Is that I can keep my speed down to 15-20mph without ever touching the service brakes. Any faster and things get a little sketchy. Between 10-15 is when the exhaust brake disengages, I'm guessing second gear and I have to use the service brakes.
With Eco-hubs installed in the same scenario as above at approximately what speed can I expect the exhaust brakes to stop working with 3.07 gears and 3.90 gears?
Drop below 35. With ECO, the trans must've relearned, bc in the same scenario, it downshifts to 3, makes the same noise, and slows below 40 pretty quickly. I feel like there is a difference as the truck stayed at 40 for longer with ECO and without having to turn off the pacbrake. So depending on grade and load, the effects will vary. I like it better bc the pacbrake is not so abrupt now, which makes sense.