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07-17-2018, 08:22 AM
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#1
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Senior Member
Join Date: Mar 2016
Posts: 169
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Exhaust Brake
I have a 1998 36 SDS
when I flip on the exhust brake my tranny goes into 4th. I get lots of braking but isn't that just engine braking as in down shifting? I didn't think that was how an exhust brake worked.
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07-17-2018, 08:31 AM
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#2
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Senior Member
Join Date: Aug 2017
Location: Warrenton, Va.
Posts: 284
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That is how mine works.
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Scott Shaffer
1998 Alpine 36 SDS
Warrenton, Va.
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07-17-2018, 09:17 AM
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#3
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Senior Member
Join Date: Oct 2014
Posts: 7,881
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Quote:
Originally Posted by TheKassman
I have a 1998 36 SDS
when I flip on the exhust brake my tranny goes into 4th. I get lots of braking but isn't that just engine braking as in down shifting? I didn't think that was how an exhust brake worked.
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Very easy to VERIFY:
Use the down arrow to 4th. Toggle exhaust brake on and off. Since the transmission is not a variable, you should be able to tell immediately, particularly if at higher RPM in 4th.
__________________
Brett Wolfe
Ex: 2003 Alpine 38FDDS. Ex: 1997 Safari Sahara. Ex: 1993 Foretravel U240
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07-19-2018, 07:58 AM
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#4
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Senior Member
Join Date: Jun 2015
Location: Alaska
Posts: 904
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From your description this is normal. In addition to Brett's suggestion, open your driver side window. You will be able to hear the change in exhaust sound as you toggle the PAC on then off.
__________________
Tim & Ruth
Alpine Coach 1999 40FDS, Cummins ISC 350
Project Restoration
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07-19-2018, 09:13 AM
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#5
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Senior Member
Join Date: Oct 2014
Posts: 7,881
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Be aware that PacBrakes DO require lubrication:
https://pacbrake.com/product/c18037-superlube/
__________________
Brett Wolfe
Ex: 2003 Alpine 38FDDS. Ex: 1997 Safari Sahara. Ex: 1993 Foretravel U240
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07-19-2018, 09:23 AM
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#6
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Senior Member
Monaco Owners Club
Join Date: Oct 2014
Location: Rigby, Idaho
Posts: 3,946
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That is how an exhaust brake works, a lot of the braking comes from downshift.
__________________
Cheers,
TonyMac
2006 Monaco Safari Cheetah 40PMT
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07-19-2018, 09:27 AM
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#7
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Senior Member
Country Coach Owners Club Solo Rvers Club iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 37,725
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Exhaust brakes work better at higher RPM's, so the transmission is programmed to downshift to keep the engine near max RPM's.
__________________
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft, HWH Active Air
Charter Good Sam Lifetime Member, FMCA,
RV'ing since 1957, NRA Benefactor Life, towing '21 Jeep JLU Rubicon Ecodiesel
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07-19-2018, 10:23 PM
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#8
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Junior Member
Alpine Owners Club
Join Date: Jun 2014
Location: Gordon,Al
Posts: 4
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PAC brake
I have a 1998 Alpine 36FDS, the pac brake hasn't worked since I bought it 3 years ago. I took it to several diesel shops and they all wanted wiring diagrams before they would work on it. One Cummings dealer told me I should leave it off, because it was hard on the engine. Any thoughts from you guys on this and does any of you have any wiring diagrams to share on this?
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07-20-2018, 05:25 AM
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#9
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Senior Member
Join Date: Oct 2014
Posts: 7,881
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Rabbit48,
Have you/they verified that the brake is not getting the electrical signal at the air solenoid?
Said another way, that the problem is electrical and not mechanical at the PacBrake.
And, if it has not been used in 3+ years, quite likely it is mechanically frozen up even if the initial problem was no electric signal.
I would not be concerned with using an exhaust brake. Virtually all trucks with the 8.3 have exhaust brakes and they use them all the time.
__________________
Brett Wolfe
Ex: 2003 Alpine 38FDDS. Ex: 1997 Safari Sahara. Ex: 1993 Foretravel U240
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07-20-2018, 06:48 AM
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#10
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Senior Member
Join Date: Jun 2015
Location: Alaska
Posts: 904
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Came across this yesterday. You may find this helpful: https://pacbrake.com/wp-content/uplo...7/08/L5046.pdf
__________________
Tim & Ruth
Alpine Coach 1999 40FDS, Cummins ISC 350
Project Restoration
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07-20-2018, 08:05 AM
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#11
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Junior Member
Alpine Owners Club
Join Date: Jun 2014
Location: Gordon,Al
Posts: 4
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Quote:
Originally Posted by Rabbit48
I have a 1998 Alpine 36FDS, the pac brake hasn't worked since I bought it 3 years ago. I took it to several diesel shops and they all wanted wiring diagrams before they would work on it. One Cummings dealer told me I should leave it off, because it was hard on the engine. Any thoughts from you guys on this and does any of you have any wiring diagrams to share on this?
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Can you verify the signal to the Pacbrake while the coach is stopped. I don't have a wiring diagram to show how the signal is routed thru the transmission, accelerator, ect.
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07-20-2018, 08:21 AM
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#12
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Senior Member
Monaco Owners Club
Join Date: Oct 2014
Location: Rigby, Idaho
Posts: 3,946
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Quote:
Originally Posted by AKOne
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Thanks for this. Reading it tells me the valve, in some applications, should close at idle rpm to help warm the engine. Start the motor, let air build, set PacBrake to ON, open engine cover and see position of valve actuator. If actuator is extended, valve is closed, PacBrake is working.
__________________
Cheers,
TonyMac
2006 Monaco Safari Cheetah 40PMT
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07-20-2018, 08:34 AM
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#13
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Senior Member
Join Date: Oct 2014
Posts: 7,881
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Quote:
Originally Posted by Rabbit48
Can you verify the signal to the Pacbrake while the coach is stopped. I don't have a wiring diagram to show how the signal is routed thru the transmission, accelerator, ect.
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NO, I don't believe you will have an electric signal with coach stopped.
Remember, the exhaust brake cuts out as you approach idle so it doesn't kill the motor.
But, wouldn't be hard to rig a test light or voltmeter and have someone sit in back while you go for a test drive.
You could also disconnect the wire to the brake solenoid and (with coach air pressure built) apply another source of 12 VDC positive to it to verify that the brake works mechanically.
__________________
Brett Wolfe
Ex: 2003 Alpine 38FDDS. Ex: 1997 Safari Sahara. Ex: 1993 Foretravel U240
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07-20-2018, 10:52 AM
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#14
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Senior Member
Join Date: Jun 2015
Location: Alaska
Posts: 904
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Quote:
Originally Posted by wolfe10
Be aware that PacBrakes DO require lubrication
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This is why love reading iRV2, always something to learn ... 
__________________
Tim & Ruth
Alpine Coach 1999 40FDS, Cummins ISC 350
Project Restoration
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