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Old 02-03-2013, 06:05 PM   #1
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93 magna, 300 cummins, exhaust brake ???

I had a switch replaced on the exhaust brake, my mechanic said it is an early and basic version exhaust brake which basically causes exhaust pressure. He suggested that at some point we should replace with a pacbrake and wire into he trans to downshift and put heavier duty valve springs.

Question is, how should I use the current exhaust brake.

Does this type of exhaust brake cause much wear and tear on the motor and exhaust?

Should I consider the switch over sooner than later?
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Old 02-03-2013, 10:24 PM   #2
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Turn on your exhaust brake and down shift your trans one gear to start, and a second if necessary to help control speed on your downhill, watch your RPM and apply brakes if necessary.
Pac Brake is just a brand name of exhaust brake. Check them out on-line.
The exhaust brake puts very little wear and tear on the engine , provided you control the RPM. No problems with the exhaust.
You would have to look into you trans type first to make sure it is programable to perform the down shifts when the brake is on.
The change up of valve springs was only recomended for P/Us with manual transmission; when I was installing Pac Brakes; before I retired; and after Cummins went to 24valve the practice stopped.
See how your current system works on the road before you spend $$$
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Old 02-04-2013, 11:50 AM   #3
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The exhaust brake is a common feature and will not harm your engine or Allison tranny.

I generally drive with it switched on except in some city street driving and on long level flat land driving. Using the EB prevents wear on your service brakes which are much more expensive to replace.

When on a steep downgrade, enter the descent at a slower speed. I usually shift to 3 gear and enter at about 35mph with the EB on. You can always speed up, but slowing down is more difficult once in the downgrade. Practice will teach you the limits of your unit. The EB assists in braking but gravity may still win and your coach will speed up. Use the service brakes to regain the desired speed.

The exhaust brake likely will not be effective below 30mph and above 60mph.

When you release the accelerator pedal, the tranny will likely downshift a gear and the exhaust brake light on your dash will light up. You will feel both events.

To determine if the EB is working try turning off the EB switch and the releasing the accelerator pedal. Then turn the switch back on and repeat the circumstances. You should note more force with the brake on.

Go to the Pakbrake web site. They have a picture of their brake there. It will show lubricaton points on their brake. Use high temp lubricant and spray it on the pivot points to keep the flapper from freezing shut due to lack of use. Having it on during most operations also prevents the flapper from seizing.

If the flapper seizes, you will notice lack of acceleration and no high speed operation from your engine.

The mechanic may have been addressing the new improved PakBrake that is available. Try yours first before buying the newer version.
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Old 02-05-2013, 04:53 AM   #4
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Thanks guys, sounds crazy to always drive with the brake on. But I assume there is some sort of mechanical thing that happens when the accelerator is released, closing the flap putting pressure back into the exhaust system. Why would this build up of pressure not hurt components like the exhaust gaskets, manifold, valves, pipes and the charged air cooler. Since exhaust can't escape does it heat things up.
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Old 02-05-2013, 12:01 PM   #5
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When I indicate the EB is "on", just the switch is on. The EB will only engage (close the flap) when there is no acceleration if working properly.

I have never had my engine temps rise when going downhill with the brake on.

I cannot provide an answer for the back pressure effects, but there are thousands of these gizmo's working every day and I have read of no ill effects.
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