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04-22-2014, 09:52 AM
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#1
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Senior Member
Spartan Chassis
Join Date: Dec 2009
Location: Reno, NV
Posts: 300
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Exhaust brake
Can the exhaust brake be applied at any speed?
I was told by the original owner not to use the exaust brake above 55 mph.
I burned up my brakes using the peddle to much above 55.
I could not get it slowed down. First time in 3 years and 25k miles I’ve had a problem. An expensive problem.
My partner with an American Dream says it’s OK to use at any speed.
You can’t hurt it. Is that correct?
Thanks, Gator, 2000 with 350 hp>
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04-22-2014, 09:58 AM
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#2
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Senior Member
Newmar Owners Club
Join Date: Oct 2009
Posts: 10,309
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Simply put, yes you can use it at any speed, the Allison TCM(Transmission control module) and the engine ECM(Engine control module) work together to not allow you to over rev the engine, or hurt the transmission. Mine is on all the time and I use it all the time.
__________________
2012 Essex 4544 2011 Jeep JK, M&G Braking, 2014 MTI 27' Hog Hauler, Wireless brake control, 2006 Ultra & 1989 Springer, 2003 Harley-Davidson
FLHR Road King Anniversary
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04-22-2014, 10:04 AM
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#3
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Senior Member
Join Date: May 2004
Location: Auburn, CA, Havasu, AZ & Mulege, BCS
Posts: 5,385
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Prior owner was misinformed
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Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project
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04-22-2014, 10:16 AM
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#4
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Registered User
Join Date: Oct 2013
Location: N VA
Posts: 202
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Yes! After putting 430K on a CAT E model, it never did any harm turning it on for mountains or slowing down, would hold 80,000 lb at 70 MPH down I 515 in Las Vegas without touching the brakes and thats a pretty good slope. Have had it on the entire length of the old La Veta Pass in Co which takes about 45 min to descend from 99500 to 6000 ft and was twisty windy 2 lane that went through downtown La Veta It is meant to be used. Turn it on. 1961: The Jacobs Engine Brake | Overdrive Retro
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04-22-2014, 10:45 AM
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#5
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Community Moderator
Newmar Owners Club
Join Date: Feb 2011
Location: Point Pleasant Beach, NJ
Posts: 31,302
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The prior owner was wrong. You can turn the engine brake on at any speed. I selectively activate it rather then leave it on all the time. First my cruise control will not engage with the engine brake on. Plus I don't want the brake slowing me down whenever I'm just coasting. That is a pain, and not fuel efficient.
__________________
Tony & Ruth........... FMCA#F416727
2016 London Aire 4519, Freightliner chassis, Cummins ISX, 2018 Jeep Wrangler Unlimited, Blue Ox Avail with AF1. TST 507 TPMS
No amount of money can buy you an extra second of time.
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04-22-2014, 06:15 PM
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#6
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Senior Member
Alpine Owners Club
Join Date: Apr 2007
Location: Concrete, WA
Posts: 842
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I leave mine on and use a light touch on the accelerator pedal to keep the exhaust brake from actuating if I want to coast.
__________________
Janet and Todd Legg
2018 Tiffin Allegro Bus 40SP
Previous RV-2006 Alpine Apex M-40FDQS
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04-22-2014, 08:38 PM
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#7
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Senior Member
Join Date: Nov 2007
Location: Charleston, WV
Posts: 3,467
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Depends! Firstly, anyone with an ISL engine does not have an exhaust brake, that engine has an engine brake. But in your case with an ISC you do have an exhaust (or PAC) brake. When it was shipped from the factory the transmission was programmed so that when you turn on the exhaust brake the transmission would attempt to select 4, but it will only do that when the engine revs are low enough not to over rev the engine. In my experience this is around 55 mph. So back to your original question both statements are sort of correct. You can switch on the exhaust brake at any speed, but it will not do anything until the speed drops to 55 mph.
Now some people have had the Allison reprogrammed so that it does not pre-select 4 but will operate the exhaust brake in any gear. I tried this and it has very little effect in 5 and 6 as these are overdrive gears. There is no harm in doing this, it just means that you have to manually move down through the gears. Truth is that the exhaust brake is not as effective as the engine brake so you will still have to use the service brakes. Getting in to a low gear and keeping the revs high gets the most out of the exhaust brake.
__________________
John and Mary Knight
2015 Newmar Ventana 4311 - wheelchair accessible
2015 Cadillac SRX Luxury AWD
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04-22-2014, 08:40 PM
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#8
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Senior Member
Join Date: Dec 2011
Posts: 442
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On rolling terrain it can be like playing a calliope.
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Jim & Elissa Edmonds
2003 34FDDS Alpine Banks 430hp #74869
Viola, Idaho 3rd Armored Cav & 3rd Infantry Division
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04-22-2014, 09:04 PM
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#9
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Senior Member
Newmar Owners Club
Join Date: Oct 2009
Posts: 10,309
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Not really true.....
Quote:
Originally Posted by Algoma
Depends! Firstly, anyone with an ISL engine does not have an exhaust brake, that engine has an engine brake. But in your case with an ISC you do have an exhaust (or PAC) brake. When it was shipped from the factory the transmission was programmed so that when you turn on the exhaust brake the transmission would attempt to select 4, but it will only do that when the engine revs are low enough not to over rev the engine. In my experience this is around 55 mph. So back to your original question both statements are sort of correct. You can switch on the exhaust brake at any speed, but it will not do anything until the speed drops to 55 mph.
Now some people have had the Allison reprogrammed so that it does not pre-select 4 but will operate the exhaust brake in any gear. I tried this and it has very little effect in 5 and 6 as these are overdrive gears. There is no harm in doing this, it just means that you have to manually move down through the gears. Truth is that the exhaust brake is not as effective as the engine brake so you will still have to use the service brakes. Getting in to a low gear and keeping the revs high gets the most out of the exhaust brake.
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I have read on here John and I was corrected before, Some of the Early models of the ISL came with a exhaust brake, so.......it could be true
https://quickserve.cummins.com/info/..._nondodge.html
http://www.irv2.com/forums/f258/engi...th-149533.html
Why does it not come on till 55 mph? A exhaust brake should come on even at 70 mph and not downshift till around 60-62 mph to the preset gear, or maybe 5th.......It should downshift when the rpm's and speed are correct for the shift, but just because it did not downshift due to speed or rpm's does not mean that the exhaust brake is not on or working correctly. Maybe what you are describing is a Alpine thing? Maybe the way they set their Coach's up?
__________________
2012 Essex 4544 2011 Jeep JK, M&G Braking, 2014 MTI 27' Hog Hauler, Wireless brake control, 2006 Ultra & 1989 Springer, 2003 Harley-Davidson
FLHR Road King Anniversary
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04-23-2014, 10:50 AM
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#10
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Senior Member
Join Date: Nov 2007
Location: Charleston, WV
Posts: 3,467
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It may be that some ISL engines had the E-brake fitted instead of the C-brake as you point out, but I have not heard of these being on Alpine coaches. I could be wrong though.
The exhaust brake is controlled by the transmission ECU and the on-off switch is merely a request to activate the brake. In experiments I did the brake did not activate until the transmission shifted down to 4. Flicking the switch on at 70mph in 6 did not activate the brake. As I said above, if yours is not programmed to pre-select a lower gear the exhaust brake will activate at any speed providing you have taken your foot off the accelerator. The programming of the ECU including what the economy button does is specific to the coach, so maybe Alpines are different.
__________________
John and Mary Knight
2015 Newmar Ventana 4311 - wheelchair accessible
2015 Cadillac SRX Luxury AWD
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04-23-2014, 11:32 AM
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#11
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Senior Member
Official iRV2 Sponsor
Overland Owners Club
Join Date: Nov 2013
Posts: 730
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I'm surprised that in exhaust brake mode that it pre-selects 4th gear. All the units I have experienced were programmed to pre-select 2nd gear when the exhaust brake activates. The brake should activate at any speed, and the transmission will downshift accordingly until it drops down into 2nd gear.
I think there are some advantages to the 4th gear pre-select, but I think the 2nd gear pre-select is more "automatic" in that the operator doesn't have to downshift manually when the RPMs drop as you slow down.
The braking force of an exhaust brake or an engine brake is greatly affected by the engine RPMs. Higher RPMs equates to higher braking horsepower, and engine brakes are able to generate considerably more brake HP than the same engine with an exhaust brake.
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Don & Anita Sweger
98 Overland Larado 4141SO
41' 325hp Cummins C8.3 Nicknamed "Lola"
Owners of: www.tvformyrv.com
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04-23-2014, 11:54 AM
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#12
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Senior Member
Spartan Chassis
Join Date: Dec 2009
Location: Reno, NV
Posts: 300
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Thanks for all the information and the great advice.
I drove about 1000 miles home from Moab Easter Jeep Safari with cracked rotors which ground down the pads. Stopped OK but not great. I used the Pac brake almost all the time and at any speed as I will in the future. I bought the front end parts in Richfield Utah , just encase I couldn’t make it home. Very stressful drive but a great jeep trip.
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04-25-2014, 05:08 PM
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#13
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Senior Member
Join Date: Jan 2006
Posts: 1,163
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Quote:
Originally Posted by gatorv
Thanks for all the information and the great advice.
I drove about 1000 miles home from Moab Easter Jeep Safari with cracked rotors which ground down the pads. Stopped OK but not great. I used the Pac brake almost all the time and at any speed as I will in the future. I bought the front end parts in Richfield Utah , just encase I couldn’t make it home. Very stressful drive but a great jeep trip.
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Sorry to hear of your issues. I think your questions have been answered. Personally, I pretty much never turn my Pac Brake off; the exception would be in significant traffic where it shifts a lot from 6th to 4th.
Were you in Canyonlands RV Park during EJS? I think there were four Alpine's.
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2014 Phaeton 36gh
2008 Jeep Rubicon or 2012 Ford F150 4x4 Lariat towds
or a couple of different trailers
Retired in Apple Valley, California
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04-25-2014, 05:22 PM
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#14
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Senior Member
Join Date: Oct 2006
Location: Rochester NY
Posts: 2,706
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Quote:
Originally Posted by Algoma
Depends! Firstly, anyone with an ISL engine does not have an exhaust brake, that engine has an engine brake. But in your case with an ISC you do have an exhaust (or PAC) brake. When it was shipped from the factory the transmission was programmed so that when you turn on the exhaust brake the transmission would attempt to select 4, but it will only do that when the engine revs are low enough not to over rev the engine. In my experience this is around 55 mph. So back to your original question both statements are sort of correct. You can switch on the exhaust brake at any speed, but it will not do anything until the speed drops to 55 mph.
Now some people have had the Allison reprogrammed so that it does not pre-select 4 but will operate the exhaust brake in any gear. I tried this and it has very little effect in 5 and 6 as these are overdrive gears. There is no harm in doing this, it just means that you have to manually move down through the gears. Truth is that the exhaust brake is not as effective as the engine brake so you will still have to use the service brakes. Getting in to a low gear and keeping the revs high gets the most out of the exhaust brake.
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Not exactly correct regarding it won't do anything until the speed drops to 55 mph.
The exhaust brake will engage immediately; the transmission pre-selects a pre-programmed gear and starts to downshift to this gear selected, but the Allison is smart enough to not downshift until the coach is at a safe RPM so as to not damage the transmission or engine.
The engine braking is most effective at higher RPM's, so you may not feel the effect of the exhaust brake until it does downshift.
Mine was pre-programmed from the factory to downshift to '2', which I found too aggressive, so I had it re-programmed to downshift to '4'. I can always manually downshift to '3' or '2' if needed.
__________________
Don
'07 Winnebago Journey 34H - CAT C7, Koni's, MCU's, SS Bell Crank, Safe-T-Plus
'07 HHR Toad, SMI AFO, Blue OX
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