Pacbrake LoadLeash P-67, Double Down Engine Brake for RAM Cummins Trucks

It was 25 years ago that the first RAM truck with a Cummins diesel engine was introduced to the world. A lot has transpired in those 25 years, not the least of which is the ever upwardly spiraling horsepower wars between the domestic auto manufacturers. In 1989, the RAM Cummins came with 160 horsepower and 400 lb. ft. of torque. Our 2014 RAM Cummins 3500 crew cab dually came from the factory with 385 hp and 850 lb. ft. of torque. The tow rating of a 1990 RAM truck with a Cummins engine was a few hundred pounds over 10,000. Our 2014 Project Hard Working Hauler truck is rated for towing 27,000 pounds. If we had opted for the 4.10 rear end gear the rating would have been 30,000 pounds.

Our truck weighs about 9,500 pounds with 85 gallons of fuel onboard (extra capacity thanks to Titan Fuel tanks), two people and a bit of luggage. If we had the 4.10 gears at full trailer rating we’re talking about a straight-off-the-showroom-floor consumer truck and trailer rig rolling down the highway at 39,500 pounds. We’re talking 50% of the maximum gross for a big rig over the road truck and trailer—serious weight and serious hauling. The combined gross weight of the original 1989 RAM Cummins was 16,000 pounds.

There are a lot of things that have contributed to the increase in payload/tow ratings over the years. Our 2014 truck is significantly stronger and beefier in every respect compared to the 1989 version. Empty, our late model truck weighs over 8,000 pounds from the factory—the 1989 version was over 5,000 pounds. A lot of that weight is in larger and more robust frame, suspension, transmission and rear end parts. But adding 3,000 pounds to the diesel RAM over the years has been more than matched by the prodigious increases in power.

We use our truck for hauling and towing and it excels in this role. Fully loaded with our 40’ gooseneck race trailer with the 4,000 pound Maulin’ Magnum race car inside along with tools, pit gear, water tanks and generator fuel tanks all filled up, we’re driving down the road with 26,700 pounds of combined gross weight. The amazing thing about our RAM truck is that it hardly notices the load. Only up the steepest grades do you have to do a little thinking ahead when planning a passing maneuver. Even up 6% grades we have no trouble maintaining the speed limit on any highway. So there’s plenty of “Go” power on tap at all times.

But, what about “Whoa” power? What accelerates must decelerate. The marvelous Cummins engine accelerates our rig, but what about the engine that decelerates it? We know, you normally don’t think of your brakes as an engine, but technically, they are. Your brakes are an engine that converts mechanical energy into thermal energy (heat) that is then transferred into the atmosphere by convection into the air flowing over the brake rotors. Typically, the brakes on a vehicle are much more powerful than the engine under the hood.

We have a good friend, the promoter of some of our favorite races in fact, who has a wife and young child. We saw them at March Meet at Famoso a couple of years ago. They had their diesel one-ton dually and 53’ merchandise/living quarters trailer with them. They were getting ready to head out to Denver after the Meet, which meant they were about to encounter a lot of steep grades. Just as our friend was about to get into their truck, for some reason he happened to look at the front wheel. Something looked a little odd and caught his attention. He looked closer and saw a large crack in the front brake rotor. His left front rotor was on the verge of complete failure. What would have happened if hadn’t glanced at the wheel as he entered his truck? When was the failure going to occur? The worst case scenario of course would have been on one of the many long downhill grades between California and Denver. We shudder to think of what could have happened.

Now, as much as we love our friend, we think he drives the wrong truck. It’s not a RAM. And it doesn’t have any kind of supplemental braking, just normal service brakes on the truck and trailer. Have you ever seen a big rig going down a steep grade with smoke pouring out of the wheels from dangerously overheated brakes? We have, many times. Ever seen a big rig with the brakes on fire? It’s not pretty. In the last year we’ve driven past the scene of two trailer rigs that were just smoldering, melted aluminum on the side of the highway. Brake failure happens, and the more you weigh and tow and haul, the more you stress your service brakes, the more likely you are to be the one with the smoking, burning brakes.

RAM pioneered factory supplement braking when it introduced the new 6.7L Cummins in its 2007 line of heavy duty trucks. If you own a 2007+ RAM Cummins truck, you have a big safety advantage courtesy of RAM innovation. If you own another brand of diesel (heaven forbid!) or a pre-2007 Cummins, then you are wholly reliant on your mechanical service brakes.

Why does this matter, what is supplemental braking? Everyone is familiar with “engine braking,” that feeling of deceleration that you get when your vehicle is in gear and you’ve lifted off the throttle. You can feel your vehicle being slowed by the engine, you can feel the deceleration and you can tell that you’re not just coasting. Engine braking occurs when the resistance within an engine is used to slow a vehicle down, as opposed to using external braking by the friction based service brakes. The advantage to engine braking is that you are decelerating without generating heat and wear on your service brakes.

It’s important to note here the difference between “engine braking” and “exhaust braking.” 2007 and newer RAM Cummins trucks come with factory exhaust brakes. An exhaust brake is, to put it at its most basic level, a potato stuffed up the exhaust pipe. An exhaust brake partially blocks the exhaust path of an engine and therefore increases the resistance within the engine and thus increases the “engine braking” effect.

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