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Old 02-16-2013, 07:30 PM   #1
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Pac brake with transmission brake?

We have a 6 speed Allison transmission with a transmission brake. I use it all the time and it works reasonably well. We live in the NW and do a lot of mountain driving. What are your thoughts of adding a Pac Brake in conjunction with the transmission brake? I know the Allison transmission is a good one, but the wear and tear on it concerns me to run the RPM's close to 2500 on a steep grade and have to keep tapping the brakes to keep the RPM's down. The truck has an on/off switch on the gear shift and I would install this same set up in the MH. Probably locate the switch next to the transmission brake switch. That way I could add additional braking to the transmission brakes by simply turning the Pac Brake switch on. You can leave it on if you want and it only takes effect when letting off the accelerator, but I usually turn it off after using it in the truck.
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Old 02-16-2013, 10:21 PM   #2
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How did you determine that you have a transmission brake? I really don't think you have one, especially on a lower end coach. Transmissions have retarders and the only production coach that I know of that has one is the Foretravel. Retarders are also found in custom coach conversions.
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Old 02-16-2013, 11:38 PM   #3
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It is a transmission brake. When you press the switch it reduces your gears one speed ie., 4th gear down to third gear (we're not talking about changing gears on the dock). A transmission brake sensor lights up on the dash and the RPM's immediately go up bringing the speed of the MH down just like a Pac Brake.
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Old 02-16-2013, 11:52 PM   #4
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Looking at our Allison manual, they call it a retarder. "when the retarder is activated, the fluid in the accumulator is pressurized by the vehicle air system and directed into the retarder cavity. The interaction of the fluid with the rotating and stationary vanes causes the retarder rotor speed, and hence the output shaft, to decrease and slow the vehicle or to limit speed on a downhill grade. There are three applications for this: brake peddle with switch, hand lever with switch, foot peddle with switch, or main switch using all three applications." We have the switch for all three applications.
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Old 02-17-2013, 12:20 AM   #5
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Here's a pdf on the trans.retarder.
http://www.allisontransmission.com/s...t=SA2953EN.pdf

Our coach has the retarder AND a Jacobs Extarder. Jacobs Extarder is just a Jacobs brand trade name for an exhaust brake. The two features work very well together.
I am not familiar with your specific coach and am guessing that it's a gas coach since you don't have an exhaust brake. I don't think you can utilize an exhaust brake on a gas engine coach.
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Old 02-17-2013, 07:05 PM   #6
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Thanks Kix, It's a 2002 37U Discovery with 330 cat. I will be calling Fleetwood tomorrow with the VIN of the coach and serial number on the Allison and see what they think. I may call Allison too. Will let you know what I find out.
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Old 02-17-2013, 07:22 PM   #7
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When I activate my PAC brake the transmission automatically drops one gear to help slow the coach.
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Old 02-17-2013, 07:38 PM   #8
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I have an exhaust brake on my Journey and the Allison 3000MH. Anyone ever add the retarder later on?
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Old 02-17-2013, 09:38 PM   #9
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Will be interested to hear what Fleetwood says - have never heard of a Discovery with the Allison Retarder installed. I don't think Fleetwood ever offered it as an option, but maybe a previous owner upgraded to it? But its not an inexpensive retrofit - the retarder is usually installed in the tranny at the Allison factory and delivered as part of the OEM tranny install.

I've only seen a few Allison Retarder installations, but they all had "RETARDER" right on the dash switch.

I see no reason why an exhaust brake could not be used in conjunction with it.
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Old 02-19-2013, 12:25 AM   #10
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/Users/CraigRinker/Desktop/IMG_5212.JPG/Users/CraigRinker/Desktop/IMG_5220.JPGWill be interested to hear what Fleetwood says - have never heard of a Discovery with the Allison Retarder installed. I don't think Fleetwood ever offered it as an option, but maybe a previous owner upgraded to it? But its not an inexpensive retrofit - the retarder is usually installed in the tranny at the Allison factory and delivered as part of the OEM tranny install.

I've only seen a few Allison Retarder installations, but they all had "RETARDER" right on the dash switch.

Hopefully these pics of my side switches come thru. I believe the "R" inside a cog is what you are talking about? Was unable to get a hold of Fleetwood today....will try tomorrow.
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Old 02-19-2013, 12:27 AM   #11
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OK..I'll try pics again.....not very computer savy!!
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Old 02-19-2013, 12:31 AM   #12
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The only manufacturer that uses the transmission retarder as factory equipment is Foretravel. It's a very expensive retrofit and it's built into the transmission, not an add on. Might even require a new transmission case.
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Old 02-19-2013, 12:35 AM   #13
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Please bare with me........hopefully this works?
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Old 02-19-2013, 12:40 AM   #14
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We have every receipt of every nut, bolt, oil change etc. that was ever put into this coach since new. There's nothing for the transmission. The switches are definitely factory installed, however, they do not coincide with the switches shown in our Discovery Owners manual. Maybe it was a special order?
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