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Old 10-25-2013, 05:31 PM   #1
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Exhaust Brake

My wife and I are just getting back to RV'ing after 15 years off (kids are now grown and on their own). Back then, it was a 30 foot travel trailer and a 4x4 Chevy truck. We just bought a Tiffin Phaeton literally last week. During the dealer's intro to the Phaeton, it was suggested to leave the Exhaust brake off unless we entered some rough terrain. Is that considered to be the correct advice out there? One example I thought of was traveling on the interstates in the slow lane and vehicles darting off the entrance ramps in front of you at lower than the traffic speed. You see that happen all the time.
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Old 10-25-2013, 05:40 PM   #2
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We only use ours when going down step hills. We connect it there and then.

We have this funny idea that the exhaust brake caused our exhaust manifold to leak since if adds pressure in this area. We could be wrong though
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Old 10-25-2013, 07:22 PM   #3
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Quote:
Originally Posted by JerryGal View Post
My wife and I are just getting back to RV'ing after 15 years off (kids are now grown and on their own). Back then, it was a 30 foot travel trailer and a 4x4 Chevy truck. We just bought a Tiffin Phaeton literally last week. During the dealer's intro to the Phaeton, it was suggested to leave the Exhaust brake off unless we entered some rough terrain. Is that considered to be the correct advice out there? One example I thought of was traveling on the interstates in the slow lane and vehicles darting off the entrance ramps in front of you at lower than the traffic speed. You see that happen all the time.

Your dealer is correct. The "Exhaust Brake" on your Pheaton is actually a transmission downshift override and not a traditional engine exhaust brake. It operates by downshifting the transmission to slow the vehicle. When you step on the accelerator the transmission upshifts to normal driving range.

During normal driving you would not want the transmission constantly downshifting / upshifting every time you released or depressed the accelerator pedal.
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Old 10-25-2013, 07:42 PM   #4
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Originally Posted by lllkrob View Post

Your dealer is correct. The "Exhaust Brake" on your Pheaton is actually a transmission downshift override and not a traditional engine exhaust brake. It operates by downshifting the transmission to slow the vehicle. When you step on the accelerator the transmission upshifts to normal driving range.

During normal driving you would not want the transmission constantly downshifting / upshifting every time you released or depressed the accelerator pedal.
Are you saying that Tiffin ONLY uses the downshift of the transmission for slowing the coach on downhill grades?

Are they using some other brand of transmission besides the Allison? If so then it might be a very "special" transmission.

That's not a very effective way to slow a coach down that weighs 35-40,000 lb's. In fact if you are going too fast the Allison won't downshift because it''s smarter than its operator. It will protect itself regardless of what setting you have the transmission pad set at.

My guess is that they use either the PacBrake Exhaust Brake, Jake Brake Exhaust Brake (or the true Jake Engine Brake which is a different animal) or the Variable Vane Exhaust Brake in conjunction with the Allison transmission.

According to the 2014 Phaeton, they come with either an Exhaust Brake or a Compression Brake depending on the engine.

2014 Phaeton Mechanical Specs | Tiffin Motorhomes

I may be wrong but that's what I think.

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Old 10-25-2013, 08:06 PM   #5
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As in all aspects of motorhoming you are going to get a full range of answers - from those who drove out of the factory gates with it on and have probably forgotten where the switch is, to those who leave it off 99% of the time.
I suspect the first group probably only blast along the interstates to and from their destination and the second group are perhaps more inclined to wander around the back roads and find the constant downshifting every time the foot comes off the throttle to be totally annoying.
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Old 10-25-2013, 08:14 PM   #6
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As far as I know, the exhaust brake is the variable vane turbo. This is coupled with the Allison transmission to give you rather good downhill braking. I normally leave mine off when traveling on flat land.
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Old 10-25-2013, 09:22 PM   #7
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Quote:
Originally Posted by JerryGal View Post
My wife and I are just getting back to RV'ing after 15 years off (kids are now grown and on their own). Back then, it was a 30 foot travel trailer and a 4x4 Chevy truck. We just bought a Tiffin Phaeton literally last week. During the dealer's intro to the Phaeton, it was suggested to leave the Exhaust brake off unless we entered some rough terrain. Is that considered to be the correct advice out there? One example I thought of was traveling on the interstates in the slow lane and vehicles darting off the entrance ramps in front of you at lower than the traffic speed. You see that happen all the time.

JerryGal,
While the folks that sold you the coach, "MAY" have SOME good insight in to the operations of certain parts/systems/components, the advice they gave you on their thoughts of operation your exhaust brake will vary widely with folks that use them on a daily basis.

In short, the primary use for them is assisting in braking, OBVIOUSLY. Now, in reality, the smartest and wisest thing you can do for yourself and your coach is, take it out and practice with it. Now, most of them are fairly good at assisting the needed braking effort in various conditions. In fact, in certain conditions, it will do about 90% of the braking up to almost stopping. They work in conjunction transmission downshifting.

And, as the transmission downshifts, it makes for higher RPMs and, thus, more efficient exhaust braking. And, the slower you go, the more it downshifts and the exhaust brake is kept at it's peak in efficiency almost, all the way to a stop sign.

Some folks don't like the way they operate as it is setup from the factory and have altered the operating characteristics of it.

But, like stated, and as another one explained to you, depending on which version of the "Exhaust" brake or, "Compression" brake you have, a smart move for you would be to simply go out and practice with it. Go down a few off ramps, some grades in your area and let it do its thing. See and feel how it works. See how good it helps your particular coach. It's good to ask and know how other people utilize theirs but, only you can determine just how much and when, you want it working for you.

The more you use it, in various situations, the more you'll learn its characteristics, good and bad. Then, YOU will be your own adviser on when you want it, and when to simply turn the switch off.

And, speaking of that, it's a "SWITCH". It can be turned on or off in the blink of an eye. So, you can use it for this minute, but, turn it off for the next city block, section of freeway, off ramp or what ever you feel you don't or won't want it operating. I flip that switch on a very frequent basis. I may want it at present and then, I see or anticipate a condition coming up that I don't want it, the switch is flipped to "OFF", THAT QUICK! So, before you go doing what the "Masses" tell you to do , and uninformed sales people, go learn it for yourself. And, by the way, about 99.99999% of them trigger the brake lights on the coach too so, be aware of that if and when you're "practicing" its usage and there is traffic behind you. Good luck with your new coach and, happy RVing.
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Old 10-26-2013, 09:49 AM   #8
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The Exhaust Braking for Cummins RV engines is more than transmission downshifting.
Quote:
Jacobs Exhaust Brake for Cummins Medium Duty Engines (Non-Dodge Applications)

More Control. Every™ Stop.

Cummins E Brake uses engine exhaust backpressure to increase your vehicle's stopping ability significantly. By restricting the flow of exhaust gases, it creates resistance against the pistons on every stroke. This, in turn, slows the rotation of the crankshaft and your vehicle.

With Cummins E Brake, your engine (B5.9, ISB, C8.3, ISC or ISL) creates up to 237 hp of retarding power to help you slow down. You use your service brakes less so they last up to three times longer. And having more braking power on long, steep hills can help reduce the risk of overheating and glazing.
Link below has a list of exhaust brake type for Cummins RV engines.
https://quickserve.cummins.com/info/..._nondodge.html
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Old 10-26-2013, 09:54 AM   #9
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Lots of suggestions and ideas. The exhaust brake will do several thinbgs for you when it is on. Chief among them is slow the vehicle down without the use of the service brakes. Seems rather silly to me to leave it off and have to use more service brakes. The other more important thing is when the exhaust brake is off the sliding vanes of the turbo can get stuck. The only way to fix this problem is to remove the turbo, take it apart and clean it. For my money, leave it on all the time, let it do it's intended job and enjoy longer brake life.
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Old 10-26-2013, 10:18 AM   #10
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If you flat tow a toad be careful when going down a long grade, the slow down mechanism + brake light signal = BRAKES ON on the toad. I came down off Tennessee Gap in Colorado to see smoking tires on toad near the bottom and had to turn off my Retarder. Lesson learned.
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Old 10-26-2013, 10:31 AM   #11
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I like to leave mine off on the highway (except for big down grades) so that the coach will roll when I get off the throttle. In traffic I like to leave it on so the it does exactly the opposite.
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Old 10-26-2013, 07:54 PM   #12
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Some of the reply's here are incredibly flat out wrong. A couple are exactly right. Please get educated somewhere else as some of these people are clueless bordering on old wives tales. Your already on the internet so go to the freightliner site or the cummins site and get your info from the builders.
By the way ; nice rig
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Old 10-26-2013, 08:00 PM   #13
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If you flat tow a toad be careful when going down a long grade, the slow down mechanism + brake light signal = BRAKES ON on the toad. I came down off Tennessee Gap in Colorado to see smoking tires on toad near the bottom and had to turn off my Retarder. Lesson learned.
According to us gear unified tow brake you hook up the toad brakes so they dont activate until you physically step on the brake pedal ; not activate with the exhaust brake. This prevents what happened to you ! Do you really have a transmission retarder?
There is an optional "retarder" for the Allison transmission, but it does a lot more than just down shift. Downshifting doesn't do much when the engine has no inherent compression braking to start with, and diesels do not.

The Allison retarder is a fairly expensive option and not often seen on a Discovery or anything else in that price class. And it certainly is not standard on that chassis.
Checking the spec sheets on the Freightliner Custom Chassis web site, I see that the chassis on the 2005 Providence included an "exhaust brake". For full details on your chassis, see 2005 Providence Chassis Specs ; "borrowed from cruiser"
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Old 10-26-2013, 09:04 PM   #14
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My switch says " retarder ", but the owners manual refers to a compression brake. Same thing?
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