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Question about 3 speed jake brake

Yahoo Message Number: 81295
On my 2000 magna, the low setting on the jake brake appears to not be working. When I set the brake on 'low' the transmission doesn't shift down to 4th like it does when the setting is at 'medium' or 'high' and I can't really detect any engine drag.
Does anyone know, should the transmission shift down when the jake brake is in the low position?

pete

2000 40' Magna #5892, CAT C-10
Pete
 2000 40'  Magna #5892  CAT C-10

Re: Question about 3 speed jake brake

Reply #1 –
Yahoo Message Number: 81296
Pete,

You might try calling the CAT hotline. The number is in this group somewhere.
The way it was explained to me for my Coach is that the "Low" setting is 2 cylinders, "Medium" is 4 Cylinders, and "High" is 6 cylinders. It downshifts in all three settings. I always just leave mine in "High"

Mark and Helen Surber
07 Intrigue 12162
C13 Cat Allison
06 Rubicon LJ

Re: Question about 3 speed jake brake

Reply #2 –
Yahoo Message Number: 81304
Mark you are correct. Folks make sure you do NOT exceed your red line RPM when you engage, you will break the engine! Rich 02 Magna 6089 C-12 cat

Re: Question about 3 speed jake brake

Reply #3 –
Yahoo Message Number: 81305
Pete, my 99' Magna does gear down to 4th on all 3 Jake brake setting.

Jim

99' Magna #5629

Re: Question about 3 speed jake brake

Reply #4 –
Yahoo Message Number: 81306
The Engine Computer will not let this happen, it will force an upshift prior to this event.

Mikee

Re: Question about 3 speed jake brake

Reply #5 –
Yahoo Message Number: 81314
I won't doubt your wisdom Mikee, but personally I won't engage over 1500 rpm and going down I break when rpms approach 2200. I will not take a chance on being protected by a computerized governor! $20,000.00 + for a rebuild ain't worth the chance. Rich 02 Magna, 79,000 miles and runs great. "ats-a my-a Bambina."

Re: Question about 3 speed jake brake

Reply #6 –
Yahoo Message Number: 81315
The Allison people say they will not overspeed the engine hang on and enjoy the ride. Bob 06 intrigue 12047

Re: Question about 3 speed jake brake

Reply #8 –
Yahoo Message Number: 81317
Actually Rich, not to beat a dead horse but I have driven over a million miles in a semi and 135000 on my 94 magna and I can assure you that it is very safe to flip the switch at any speed or rpm and the transmission and engine works together very well. Just putting in my 2 cents worth LOL

Dave coach # 5158

Re: Question about 3 speed jake brake

Reply #9 –
Yahoo Message Number: 81318
? It will even upshift into neutral if necessary to prevent over revving. Imagine heading out of control down a steep grade with the Allison upshifting into neutral. But then the math says that you would be doing 98 mph in 6th gear at the time and have a lot more problems than just the upshifting. But whatever happened to you at the bottom the engine would be fine. Comforting huh.

Don Seager

2004 Allure 31046

Re: Question about 3 speed jake brake

Reply #10 –
Yahoo Message Number: 81322
This may be true on most engines but not on the C-12. The redline for a C-12 is 2120 rpm. The Allison 4000 is set to upshift at 2500 rpm. There has been a lot of discussion on this on the CAT Yahoo site. Look at message #14950 and the messages attached to it.

John

#11810 with a C-12 that has exceeded the redline with the Jake on.

Re: Question about 3 speed jake brake

Reply #11 –
Yahoo Message Number: 81333
My coach has a C13 that has a plate on it that is stamped Max RPM 1800. The exhaust brake is built into the engine on the C13. Several times I have hit 2300 RPM when it downshifts at which point I stab the chassis brakes and lower my speed to a point that is within the RPM range. I was told by the tech at CAT that the engine control module won't allow the engine to overspeed or send the signal to transmission to allow it to downshift to a range that would hurt the engine. The tech at CAT also said the engine could handle 2300 RPM when engine braking. He said that the controllers are linked and that it won't do anything that will harm it.
I still jump on the coach brakes and slow it down to bring the RPM's back because it scares me.

Mark and Helen Surber
07 Intrigue 12162
C13 Cat Allison
06 Rubicon LJ

Re: Question about 3 speed jake brake

Reply #12 –
Yahoo Message Number: 81335
I just pulled out my Caterpillar engine manual dated July, 2004 and it states: Notice:

"Do not exceed 2300 RPM in any situation or 2100 RPM If equipped with an auxiliary engine brake system"

1800 RPM seems pretty low for a maximum RPM doesn't it??

Fred Compton

2005 Magna # 6454 w/ Cat C13

Re: Question about 3 speed jake brake

Reply #13 –
Yahoo Message Number: 81340
I guess if I was having these rpm issues with my coach I would go to an allison transmission shop and see if they could set the transmission up to match the engine. I am not positive but I am pretty sure that is possible. If anyone knows for sure I would be interested in knowing. Thanks.
Dave 94 Magna #5158

Re: Question about 3 speed jake brake

Reply #14 –
Yahoo Message Number: 81341
The issue depends on wether fuel is being applied at a given RPM. Red line limit with the engine

working is as you said 2120 +/- a few. When the engine is free wheeling with no fuel applied its much

higher. What you don't want to do is step on the accelerator while the engine is in the breaking mode

above 2100 rpm. That forces the tranny to up shift and the chance of some confusion on the engines

ECM and the potential for harm.
TWI 2004 Intrigue 11731

Original Message:
-----------------

From: jocsoc2000 jocsoc4@... Date: Thu, 02 Aug 2012 15:54:02 -0000 To: Country-Coach-Owners@yahoogroups.com Subject: [Country-Coach-Owners] Re: Question about 3 speed jake brake

This may be true on most engines but not on the C-12. The redline for a C-12 is 2120 rpm. The

Allison 4000 is set to upshift at 2500 rpm. There has been a lot of discussion on this on the CAT Yahoo site. Look at message #14950 and the messages attached to it.

John

#11810 with a C-12 that has exceeded the redline with the Jake on.

Re: Question about 3 speed jake brake

Reply #15 –
Yahoo Message Number: 81343
On Some Cat Diesels the 1800 RPM is the running high torque speed. Anyting over 6 percent will be an Overspeed. Gensets only. I would not worry but keep it Below 23/2500 RPM. Does your Tack have a redline marker? Ken Retired Cat Tech. My Cummins redlines at 2650 RPM bet a Different Power House. BTW Jake Brakes can be Troublesome and when Cat Does overhead valve and Injector Insp./Adj. Have the Jake Brake Rockers checked. I remember our Low Boy Tractors had lots of Issues but they put Hundred of Thousands of miles delivering and picking up Eqpt. Ken 99 Allure 30356.

Re: Question about 3 speed jake brake

Reply #16 –
Yahoo Message Number: 81378
John,

How do you look up the message on the Yahoo CAT site. I am not real familiar with Yahoo Groups. I tried search for CAT and got a lot of feline lovers (some rather strange) groups.
Mark

Question about 3 speed jake brake

Reply #19 –
Yahoo Message Number: 81339
Thank you Fred, I have been mildly hammered by Technicians and coach owners repeating over and over, "Don't worry about it" the transmission or a computer will not allow a over-rev. I know I read that in one of the epistles that come with the coach, .."Do not exceed 2300 RPM in any situation or 2100 RPM If equipped with an auxiliary engine brake system" "Do not exceed 2300 RPM in any situation or 2100 RPM If equipped with an auxiliary engine brake system"
I also had Cat tec's confirm it. If I'm doing 1500 rpm and select two cylinders the engine revs-up immediately, four cylinders less quickly, six cylinders it caps out at 2000 rpm's. If the hill is causing any increase I break, if I'm caught going down hill over 1500 rpm say 1800 or 2000 rpm, I will break down to 1500 and activate all six cylinders. If the grade decreases I'll decrease to 4 cylinders, and rarely at a long slight down hill, I'll decrease to two.
Take it or leave it, your choice! Rich Villa 02 Magna C-12

Fw: [Country-Coach-Owners] Re: Question about 3 speed jake brake

Reply #20 –
Yahoo Message Number: 81344
Rich,

My experience is the same as yours.
My 2003 Magna has the C-12 with Allisson 4000. Engine documentation says to not exceed 2100 RPM if equipped with Jake. My setup definitely exceeded 2100 RPM in fourth gear descending the Rockies. My 2004 Allure never did that in 120,000 miles.
For some reason the C-12 Allisson 4000 combination does not self protect.

George in Birmingham(still in Santa Fe) 'O4 Magna 6298
George in Birmingham
2003 Magna 6298
 

Re: Fw: [Country-Coach-Owners] Re: Question about 3 speed jake brake

Reply #21 –
Yahoo Message Number: 81351
I had an 05 Magna with a C13 Cat and when I engaged the engine brake, it would shift the trans into 4th range and then to 4th gear. I liked the braking function as the engine RPM would say at about 2000rpm, keeping the coach at about 50 mph down a hill. I traded in in for an 08 Magna with a 15 liter cummins and have had problems with the engine brake as it shifts to 3rd range and then to 3rd gear and over rev's the engine (2400rpm) on down grades, as it shifts all the way to 3rd gear. This is not suspose to happen per the CCI manual as the transmission is suspose to stay in a higher gear than 3rd when the engine rpm exceeds the max allowed . I just had the trans. reprogramed to not allow the trans to shift to a lower gear during engine braking. Now, when I engage the engine brake, I MANUALLY reduce the trans gear range as needed to slow the coach witout over reving the engine. It works very well as I can control the decent speed down a hill at my desired speed without over reving the engine. Hope this helps all who are trying to keep your engine RPM at or below the max and still be able to decend a hiil at your desired speed.

John
08 Magna