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Exhaust Brakes For the Dodge/Cummins Ram
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My Pacbrake comments
Other Pacbrake comments
PacBrakes and the ISB
Cummins Rambrake
Jacobs E-brake
BD Engine Brake
David Gentry's BD comments
US GEAR D-Celerator
Stan Steele's D-Celerator Comments

From the FAQ:

If a diesel engine has higher compression than  a gasoline engine, why doesn't it have better "engine braking"?

On any 4 stroke engine (intake-compression-firing-exhaust) the piston requires torque from the crankshaft to compress the air in the cylinder during the compression stroke. That compressed air re-expands producing almost the same torque during the firing stroke (there is some pressure lost as heat through the cylinder wall and head). Thus, there is no "compression" braking on a four stroke gasoline or diesel engine.

So what is the source of the braking effect when I lift my foot with a gasoline engine?

When braking,  a gasoline engine works against a closed throttle plate which restricts the amount of air that can enter the cylinder during the intake stroke.  Crankshaft torque is used to pull the piston down against the atmospheric pressure in the crankcase which is attempting to keep the piston at TDC  because the air can't come through the restricted opening fast enough to fill the cylinder.

Atmospheric pressure is about 14.7 psi (against a perfect vacuum) which works against the area of the piston. In a theoretical 4" bore X 4" stroke engine, the piston has an area of 12.5 sq in resulting in 185 lb of atmospheric force resisting the piston under ideal conditions.  A hypothetical 4" stroke would act with a 2" lever against the crankshaft producing a maximum of 30 lb-ft of braking torque (actual brake torque is considerably less).

Thus it is the vacuum above the cylinder on the intake stroke that causes you to slow down and gasoline engines are really taking advantage of "vacuum braking."

But what about the diesel?

When decelerating, the diesel engine operates effectively at atmospheric pressure without a restriction on the intake and exhaust manifolds. Without a restriction in the plumbing,  the diesel engine offers considerably less engine braking than a gasoline engine.

An exhaust brake uses a butterfly valve behind the turbocharger or in the exhaust pipe to restrict the flow of exhaust gas. When the valve is closed, the butterfly restricts the exhaust flow much like the old "potato-up-the-tailpipe" and holds a maximum of 30 to 60 psi at the exhaust manifold.  This forces the engine to act like a large air compressor and results in engine braking better than many gasoline engines can produce (remember, the gasoline engine only has 14.7 psi from the atmosphere, while the diesel exhaust brakes easily double that).

For the Cummins B installed in the Dodge Ram pickup, there are several makers of exhaust brakes for people who tow or haul heavy loads in hilly terrain.

A descriptive picture of exhaust brake operation can be found at the Riker Products web page.

JAKE BRAKES: An exhaust brake is not a "Jake" brake.

There are several makes of Ram exhaust brakes:


Dave Fritz's Comments and Excerpts From Mailing Lists:


I have the Pac Brake with the stock 30 psi valve springs. The brake sounds like a wheezing/whistling/stopped up catalytic type of noise and isn't loud enough to be affected by "Jake Brake" regulations in town. The braking noise is probably no louder than the engine is at 3/4 throttle. It doesn't sound anything like a "Jake"


The Pac Brake on the B provides more effective engine braking than my F250 with the 460cid gasoline engine (I have compared the two load-for-load on some local "hills"). The brake also works well with the cruise control by holding the truck back on long steep grades with the brake cycling on and off as necessary. At less than 9800 lb GCVW, the Pac Brake/cruise control will hold 57mph (set at 55) on a 1.5 mile 7% down-grade in OD without the use of the brake pedal.

For two years I did not use a brake controller for my farm trailer, although the GCVW with a loaded truck and trailer had reached 14,800 lb several times. The PacBrake was effective enough that I could easily control the trailer although with heavy loads, some mild brake smoke was evident on occasion.

FWIW, I leave the brake switch on most of the time, and now have 55,000 miles on the original brakes with plenty of lining remaining.

The 60psi Pacbrake requires an exhaust valve spring upgrade but produces more than twice as much braking effect. So far I have not felt that I needed the extra braking. More pressure = More noise? - I don't know, but the PacBrake on Sue's 2001 ETH does not seem to be louder.


There are claims that the turbo-mounted brakes cause excessive exhaust restriction.  The contention is that turbo-elbow mounted exhaust brakes impair engine performance, safety, and durability.    Arguments can be found on www.dieselpage.com/usgalert.htm,  on Us Gear's argument against turbo mounted exhaust brakes, and in postings to the mail lists.    Read the mail list exhaust restriction claims and counter claims, then decide for yourself which point of view is valid for your operating conditions.


Both The Pacbrake and the Rambrake are vacuum engaged, replace the turbo exhaust elbow, and bolt in easily.

At a Cummins open house (1996), Cummins service people installed one on their truck as a demonstration and told us that there was no power penalty because the restriction is not significant with the wastegated turbocharger. They did not make any fuel injector pump adjustments to compensate for the brake.

The installation instructions were not included in my Pacbrake box (I bought it at the open house and the instructions must have been removed to show to someone) but I figured out how everything went together anyway by looking at some TDR pictures.

A few miles of driving and periodic stops to adjust the throttle position switch with a screwdriver were all I needed to set the brake sensitivity. The brake's turbocharger elbow, that replaces the factory elbow, has a convenient plug for a pyrometer sender.

I originally noticed that the PacBrake would use all of my vacuum reserves in cold weather and leave me with no vacuum boost on my power brake. I thought that, given the well known vacuum inadequacy of the vacuum pump on grades with trailer, that this was to be expected. While attending the 1997 TDR Rally in Mesquite NV, I had the opportunity to talk with a PacBrake representative. When I mentioned the cold weather problem, he replied that this was NOT normal. Just on my word alone Packbrake sent me a new vacuum cylinder because they suspected that mine had a bad seal. They never sent me a bill or even asked for proof that I was still under warranty. I wish all businesses stood behind their products like that.


Pacbrakes are priced in the 600's now, but check the Pacbrake page for the latest price. Shows, rallies, Cummins open houses often have them at discounted prices.

Problems With Older PacBrake Versions

After 3 years and 35,000 miles under the hood in the elements, my throttle switch began sticking and the brake would not always engage. At the 1999 TDR rally, I bought a replacement switch which mounts under the dashboard - the same arrangement used for ISB engines. This new location protects the microswitch from vibration, water, and dirt.

The replacement kit contained a new switch, a jumper to replace the old throttle switch, and a jumper to connect the new throttle switch to the existing power switch. A nut beside the steering column is removed, the switch bracket is placed on the under the stud, and the nut is reinstalled.

  Switch and bracket    nut to be removed     switch mounted  

Other Pac Brake Comments

Subject:    Re: DiRT: Exhaust Brakes
Date:        Tue, 1 Sep 1998 20:51:13 EDT
From:       Drdonnelly@aol.com
To:           DiRT

I still like PacBrake, and not just for the price.

The reason for more than one brake is that (1) you can use more braking force with bigger exhaust springs, so Pac takes advantage of it; (2) the automatic without torque converter lockup switch gives poor braking, so the butterfly compensates with less bypass effect than for 5 speeds.

If you use the switch on the AT, the manual trans brake works well.

I usually keep an extra of the 24 valve PacBrake around, C14024.  By enlarging the butterfly holes, it can be used on even the 12 valve 5 speed with 30 lb springs.

Subject: Re: [RAM] Diesel engine performance with a Rambrake installed
Date: Thu, 14 Aug 1997 22:49:12 EDT
From: packmanjim@juno.com (JAMES B. DAVIS)
To: RTML, cummins

Ron! I`m strictly an ameteur when it comes to mechanics but I have as Pac Brake on my `95, There was no Ram Brake then, but the difference in them is minute as near as I can tell. If my performance suffered It wasn't enough to notice and the benefit is so great that I cannot shout it loud enough. These brakes should be standard equipment. While traveling in the mountains throughout the west , and there are some HIGH ones, My brake has saved me enough worry that I could sell them if I wasn't retired. So Put the brake on and relax coming down those hills. P.S. My truck has an automatic and they tell me that on the stick it even more effective. Jim

Subject:   Re: DiRT: 1999 Questions
Date:       Tue, 25 Aug 1998 11:52:16 -0700
From:      "Paul R. Haller" <phaller@uclink4.berkeley.edu>
To:          DiRT
 Two hours is about right to install the brake <I did it a month ago> but on the engines requiring valve spring replacement give yourself 4-6 hours if you have never done it before and you'll need to buy a spring compressor too. Do not even attempt the replacement without previous engine experience. You will probably lose the valve inside the engine if you don't run the cylinder you are working on up to TDC.  All the work is worth it when you activate the brake for the first time and the truck and trailer coast to a stop without ever touching the brakes.
                                -Paul R. Haller-

Subject:  Re: DiRT: 1999 Questions
Date:      Tue, 25 Aug 1998 12:35:20 -0700
From:     "Paul R. Haller" <phaller@uclink4.berkeley.edu>
To:         DiRT

> US Gear Corp Makes a D-Celerator  which fits most
> popular Diesel tow Vehicles.
> Any experience, advice regarding this product?

 The US Gear unit is electrically activated using a solenoid and uses a fm transmitter to activate the brake rather then vacuum. The solenoid creates about 40 psi to open the butterfly where the Pac uses vacuum and creates 75 psi opening force. The electric engagement of the U S Gear decelerator can be further degraded by salty roads and poor electrical connections at the brake itself or at the relay. I like the 2nd butterfly design but I don't like cutting the exhaust system to install it. The Pac , BD brake, and Jacobs all install in place of the elbo.  Pac and BD offer a 2 year warranty and a 30 day money back satisfaction guarantee while US Gear offers 1 year guarantee.

 The brake is actually in operation a very small percentage of total driving time and ,as a result, performance while open is often more important then when operating. The Pacs performance in the exhaust stream is excellent and creates no back pressure and in cross section is larger then the stock elbo. The BD is about a wash as compared with the stock elbo and the Jacobs is smaller then either the BD or Pac...I am not sure about the US gear.

 After looking at all 4 brakes I decided on the Pac or BD.  I like the BD ability to create more back pressure at lower rpm and it's well made.  I ended up buying the Pac primarily because of its price and its features.  BD brake was about 1100$ and Pac was 685$.  Too much of a difference to ignore.  I am extremely satisfied with the Pacs ability to slow my 15000 lb. 5th wheel and would highly recommend it to all who need additional braking.
                           -Paul R. Haller-

Subject:    Re: DiRT: 1999 Questions
Date:        Tue, 25 Aug 1998 22:48:07 -0400
From:       Mike Frenchek <mfrench@voicenet.com>
To:           DiRT

I would advise against the D-Celerator.  I met a fellow Rammer on vacation in Colorado and his D-Celerator would often stick in the closed position. This really hinders your power!!!  He would have to pull off the road and let the exhaust system cool for a short period to have it release.  He told me that the butterfly valve in the unit closes tightly against the inner sleeve and sticks with heat expansion.  I hear the Jacobs has the same tight operational tolerances.  The Pac leaves a uniform space all around and never touches the sides therefore no sticking.  The Pack also has positive vacuum activation for both closing and opening.  The Jacobs has a spring return.  The job would be well within your experience level.  Have fun!


Subject:     Re: Exhaust Brake
Date:         Fri, 25 Dec 1998 06:58:51 -0800
From:        "jgeorge" <jgeorge@inreach.com>
To:           cummins

I don't think you can go wrong with any of the popular exhaust brakes. I'm using a Pacbrake on my '95 2500 CC auto and it works fine. The only additional feature is a manual switch to lock the torque converter clutch. The brake I have is the model that does not need the heavy valve springs so it really doesn't brake as much as the other Pacbrake or the Jacobs. Just as a test I went from Eureka, CA to Redding, CA via state route 299 towing my 32' 1980 Traveleze (heavy old thing). I was able to go from US101 to Redding without using the service brakes except for stopping in Weaverville and Redding. If you are familiar with that road you know that there are some really steep and crooked places. And long down grades. I dropped it to second before going down from Buckhorn Pass (a couple of steep 20mph turns) but that was the only place that just locking out OD was not enuff. I don't need the service brakes going down the Donner grade eastbound on I80. So any of them will work just fine.


PacBrakes and the ISB

Shortly after installing a PacBrake on his 98 Ram ISB, Pete Wells reported that his engine would set a fault code, illuminate the check engine light, and the engine would no longer respond to the throttle. Numerous trips to the dealer finally isolated the problem to the PacBrake switch, which had just enough mechanical pressure on the throttle linkage to prevent the throttle from seating in the idle position. The microswitch mounted to the throttle linkage will not work with the ISB.  

The Pacbrake kit for an ISB now uses a micro switch that fits under the gas pedal instead of mounting on the linkage under the hood. There have been no more problems with ISB engines with the new switch. Sue has one on her 2001 HO diesel (ETH).

Cummins now has their own "Rambrake" manufactured by Jacobs for RVs and Dodge Rams equipped with the B5.9. The company claims it is more effective at low RPM than the Pacbrake is. It also uses a return spring instead of vacuum to disengage, making it more reliable when the vacuum is low.

The cummins part number for 94+ trucks is 380484, and includes the required 60 valve springs. Pre 94 trucks also need a number 3804854 exhaust pipe header kit. I don't know what they cost. Installation is probably similar. Consider joining the Power Boosters Club for the 10% discount before you buy a brake.  

POSTED TO THE CUMMINS LIST by Josh Berman, a Cummins employee.

Subject:  Re: [RAM] Diesel engine performance with a Rambrake installed
Date:      Tue, 2 Sep 1997 07:57:08 -0500
From:     Josh Berman <j.e.berman@metc.cummins.com>
To:         cummins

Hello everyone,

Here's a pretty old thread I just got an answer for. I spoke with a performance engineer who helped to develop the Rambrake. He said that because the exhaust brake butterfly is so close to the outlet of the turbo, the exhaust flow is too turbulent (not to mention warm) to get an accurate pressure drop measurement.

They had to run the engine in the test cell and in trucks with the stock elbow and then with the exhaust brake (off) to compare performance. He said that the performance difference (if there even is one) between the stock elbow and the brake was not measurable.

Josh Berman
Subject:  ISBs, RamBrakes, & Dodge trucks
Date:      Tue, 13 Jan 1998 09:24:38 -0500
From:     Josh Berman <j.e.berman@metc.cummins.com>
To:         cummins

The ISB engine (in both RVs and Dodge trucks) does come equipped with 60 pound springs for the brake. As far as warranty goes, I don't know of anyone who has had warranty problems because of installing a brake other than a RamBrake, it's just that we have an agreement with Dodge that the RamBrake definitely doesn't void the warranty.

There is a "new" version of the RamBrake on the way for the ISB engine. It has a different sized orifice in the brake so that the braking force is the same or better as the "old" RamBrake on the 2-valve product.

At the present time, the engine-mounted ECM will NOT control the RamBrake, or any other exhaust brake, on the Dodge truck. The brakes will still have to be set up with the microswitch touching the throttle bellcrank (even though the throttle input to the ECM is electronic, there's a cable running from the throttle pedal to the bellcrank which is mounted above the
fuel pump. That bellcrank has a TPS on it, and the TPS sends a signal to the ECM).

On RVs, and other vehicles that don't use the "Dodge" (in "'s because it isn't made by Dodge, it's just used on ISBs in Dodge trucks), the ECM CAN control an exhaust brake.

        -Josh Berman

Jacobs Ebrake  

 Information will be posted as it becomes available.  

BD Engine Brake

BD claims to be the only TURBO MOUNTED exhaust brake with FULL PRESSURE regulation!  Vacuum activated and easy to install.

Subject:   DiRT: Exhaust brakes compared
Date:       Tue, 25 Aug 1998 18:57:47 -0400
From:    "David Gentry" <dgtech@erinet.com>
To:          Dirt

I, like several others, have been searching for the best exhaust brake for the money.  I have decided on the BD brake because of its ability to produce more retarding horse power in a useable RPM range.  The following figures were sent to me by each of the manufactures.  You can make up your own minds.  All figures are with the 60# springs.

The following are the RHP(retarding horsepower) as given by the manufactures via e-mail:

1800 130 60 NA
2000 140 70 75
2200 150 85 96
2400 155 103 113
2600  160 120 134
2800 160 140 156
3000 or 3100 160 188 190

As you can see, the BD brake produces much more hold-back power in a useable RPM.  I did not want to go to red line to get the maximum braking power. The BD does produce the most braking power up to 2800 rpm.

I hope this helps a few of you. The figures speak for themselves, in my opinion.  I am paying about $300 more for the BD over the PAC, but my life and engine are worth it,  The RAMBRAKE cost about the same as the BD.  Both are around $1300.The PAC could be installed for $1025.

I am having it installed on September 11.  I have a big trip planned for New England at the end of September.  Feel free to e-mail me after October 15, if you want to hear how it worked with my Ram with auto. and a 10,000# fifth wheel in tow.

US Gear D-CELERATOR Brake Operation
D-Celerator operation Sketch of D-Celerator installedU.S. Gear's Diesel Exhaust Brake increases braking power and helps extend brake life. Push button activated, a stainless steel butterfly valve closes on the D-CELERATOR to create instant back pressure on your diesel engine and gently assists your vehicle's brakes. A turbocharger-type bypass port allows excess pressure to escape, preventing engine stall-out or damage

Subject:    DiRT: Exhaust brakes
Date:        Wed, 26 Aug 1998 09:34:23 -0500
From:       "Stan Steele" <sss@moment.net>
To:           DiRT

I have had a US GEAR D-Celerator  (4") on my 95 3500 4x4 5sp and put 165K on it with a TST #5 plate and plenty of other goodies. Then I put the same D-Celerator on my 97 3500 4x4 5sp with TST #5 plate and have 170K on it now, at NO time has it ever stuck or had a malfunction in over 300K miles! If you know the smoke that a TST #5 plate can make if it would stick I am sure mine would have done it. On the other side if you want to or are making any power over stock with all other E-Brakes you will close your exhaust down to 2" ID or less so the only E-Brake for the Power user  is the US GEAR. I don't want to start an E-brake WAR but if you do the math you know this is the truth and most people are not aware of the restriction that is in the other E-Brakes. I have driven trucks with all the other E-Brakes and they work good for the normal driver, so pick a brand and go with it.

Stan Steele



Last Update April 9, 2001