Pacbrake C44074 DirectMount PRXB Max Flow Exhaust Brake

1998.5-2002 Dodge 5.9L Cummins (Manual)
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Pacbrake’s flagship product, the PRXB (pressure regulated exhaust brake), is the unquestioned leader in the supplemental brake industry. The patented PRXB design delivers the strongest braking horsepower, greatest speed reductions and shortest stopping distances possible without the use of service brakes. It maintains optimum retarding performance by maximizing the exhaust backpressure throughout the entire RPM range. Unlike a typical exhaust brake, which requires high RPMs to work properly, the PRXB delivers constant exhaust pressure (braking) as early as 1200 RPM through to the maximum allowable RPM.

Controlled by a master ON/OFF switch, Pacbrake’s exhaust brakes provide whisper quiet supplemental braking that allows service brakes to be used much less, ultimately saving you money. They have the ability to be left on all the time, making it ideal for in-city driving or for steep, downhill grades. This product pays for itself as less wear on the brake pads means fewer brake jobs.


In order to have consistent and effective braking over the entire RPM range, it is important (and necessary) to maintain constant backpressure. To achieve this, Pacbrake’s patented design has incorporated an additional waste gate on the butterfly valve to regulate the amount of exhaust flow that is being passed through. The flow is controlled by a spring-loaded arm, whose pressure rating and location are key factors in the functionality of the PRXB. Located outside of the housing and away from the heat, the spring is able to maintain its strength and durability for years of proper and precise braking performance.

Backpressure is created by exhaust flow entering the housing, hitting the closed butterfly valve and being forced back out in the direction it came. It is maintained by the pressure-controlled spring that is located on the outside of the exhaust brake housing.

As the engine’s RPM increase, the spring compresses and the arm moves away from the butterfly valve, therefore releasing more exhaust flow through the orifice. As the RPMs decrease, the spring releases and the arm applies pressure back onto the plate, covering the hole, and ultimately releasing a smaller amount of exhaust flow.

There is less than a 10% change in backpressure over the entire RPM range on the PRXB

This 4" PRXB Exhaust Brake is designed with a unique cast housing specifically for 1994-2002 Dodge Ram trucks (equipped with 5.9L Cummins diesel engines and HX/HY35 turbos). Integrated with the patented PRXB design for the most braking horsepower at low engine RPM's, this brake is engineered to reduce the use of your service brakes while maximizing the exhaust flow. The 'maximum exhaust flow design' allows waste gate gases to escape the engine faster and spool the turbocharger faster to decrease turbo lag. In turn, this increases horsepower and torque while lowering EGTs (exhaust gas tempatures). The brake's 5 bolt flange bolts directly to the turbocharger outlet (Directmount™ design) eliminating the restrictive factory flange. Exhaust pipe adapters are available to fit factory and all larger aftermarket exhaust systems.

Features & Benefits:
  • PRXB Delivers Strongest Braking Horsepower
  • Less Wear & Tear On Service Brakes 
  • Ideal For In-City Driving Or Steel, Downhill Grades
  • Mounts To Stock Turbocharger

Vehicles with aftermarket 4" O.D. exhaust systems will require (1)  C11342 adapter. (see below).

C14004 Clutch Switch required on 1998.5 models.

Mfg. Number:

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(1 Rating, 1 Review) Average Rating:
Xtreme customer service, great product
Jay (Phoenix, Arizona) 5/13/2014 11:02 AM
The Service: When I called to check availability, Jeremy gave me his contact information, asked me to hold, called the the factory and gave me a conservative delivery date. When I opened the valve assembly, I was convinced (wrongly) that it was totally different than the elbow in my truck. I called and they were both patient and helpful. The Product: Installation instruction are clear and precise. Everything I needed was included. It is definitely a two man project. You will need access to a welder. I took two of us almost a full day to install. In 5th gear, with a 7,000 pound trailer, my truck accelerated to 63mph on a 6% grade. In 4th gear the truck decelerates on the same grade. I noticed a performance increase with the exhaust brake. With the added weight of full water tanks (308 pounds) I climbed the grades with less effort.