Exhaust Brake 'Mode" in the "Cruise Control Perimeters"

[stuplich@ymail.com]

On some, (most?, all?), of the electronically controlled Cat powered Safari coaches, (with the Allison MD3060 6 speed and a PacBrake), the "Exhaust Brake Mode" in the "Cruise Control Perimeters" of the Cat ECU, (Electronic Control Unit), can be set to any 1 of 3 modes:
1.) MANUAL MODE
2.) COAST MODE
3.) LATCH MODE

Originally, (as it came from SMC). my '96 was set to MANUAL MODE".
In 2012 had a Cat shop change it to "Coast Mode', (which I used for a year).
In 2013 I had it changed from "COAST MODE" to "LATCH MODE", (which I prefer).

When programed to "LATCH MODE" this is how/when the Pacbrake operates, (if/when the Pacbrake ON/OFF switch is in the ON position):
The PacBrake remains OFF until/unless the service brakes are applied.
Application of the service brakes turns the PacBrake ON...And the cruise control OFF
Tapping the throttle pedal, (or accelerating), turns the PacBrake OFF.
If/while ONLY the accelerator pedal is used the cruise control operates as it should.

[wolfe10]

Mel,

I don't have my manuals with me right now, but I believe you are describing LATCH MODE-- also my favorite:

Latch Mode* – allows use of exhaust brake when you need it and COASTING when you don’t
When throttle is closed – Coast
When throttle is closed and service brake applied, the exhaust brake comes on. It stays on whether you continue to use service brake or release service brake.
As soon as you apply any throttle, the exhaust brake turns off.
*Requires brake input signal to ECM

[TDJohn]

Mel and Brett,

Here is a copy and paste of a post Mel posted back on December 1st of 2016 regarding the modes. I have not read the manual, because I have no need to, so I don't know how accurate this info is, but it sounds like Brett is correct.

[copy of Mel's post]

"On electronically controlled Cat powered coaches the exhaust brake mode in the ECM can be programmed by a Caterpillar Dealer to operate in any 1 of these 3 modes:

1. Manual Mode: operates the Pacbrake manually at the driver’s discretion.

2. Coast Mode: engages the Pacbrake when the service brake pedal is applied and
disengages when the pedal is released.

3. Latch Mode: engages the Pacbrake when the service brake pedal is applied and
remains on after the pedal is released. The Pacbrake disengages upon activation of
another input such as depressing the throttle or clutch, or when engine speed
drops below 800 RPM or when the Pacbrake switch is turned off.

I believe most coaches come preset to Manual Mode, (mine did)...however I
prefer Latch Mode.

Mel
'96 Sahara, 3126 Cat, MD3060 Allison, Pacbrake"
[end of Mel's post]

On a slightly different note, I wish there was a mode, or a way to be able to turn the Allison pre-select feature on and off as needed. If that were possible I would choose 2nd gear pre-select for city driving and no select (no forced downshifting) when going down long steep mountain grades. This would allow one to pick a gear that you need and use the pac brake as needed, without the transmission trying to continuously downshift into lower gears (this would eliminate gear hunting, each time the pac brake is applied and released). It would be nice if an after market company would off this kind of program...

[Safaritoonces]

Is there a way to set the exhaust brake mode to "Latched" without having Cat program it. Here the Cat min cost is a few hundred dollars.

[stuplich@ymail.com]

Brett and John
Thanks for catching that mistake.
My message original message has been edited/corrected to read:

"Originally, (as it came from SMC). my '96 was set to MANUAL MODE".
In 2012 had a Cat shop change it to "Coast Mode', (which I used for a year).
In 2013 I had it changed from "COAST MODE" to "LATCH MODE", (which I prefer).

When programed to "LATCH MODE" this is how/when the Pacbrake operates, (if/when the Pacbrake ON/OFF switch is in the ON position):
The PacBrake remains OFF until/unless the service brakes are applied.
Application of the service brakes turns the PacBrake ON...And the cruise control OFF
Tapping the throttle pedal, (or accelerating), turns the PacBrake OFF.
If/while ONLY the accelerator pedal is used the cruise control operates as it should."

Sorry about the mix up

[TDJohn]

Is there a way to set the exhaust brake mode to "Latched" without having Cat program it. Here the Cat min cost is a few hundred dollars.

Robert,

It is possible that Dave Atherton (605-997-0720) might be able to reprogram your cruise control, but he is located in AZ, so you would have to do it during your travels.

[stuplich@ymail.com]

Is there a way to set the exhaust brake mode to "Latched" without having Cat program it. Here the Cat min cost is a few hundred dollars.

Safaritoonces
I suggest you call different Cat dealers/shops as you travel.
(A Cat dealer in central Wisconsin charged me nothing for that change in perimeters and a 3 page printed readout).

[05wingrider]

Thank you to Mel, Brett & John
I've wondered about being able to change the parameters of the pac brake (now that I have mine working) but wasn't sure what I wanted since I wasn't able to find a clear (to me) definition that other's have used. I think I'll be going over to my local Cat repair facility this winter and talking to their guru's and see how pricey it is - Latch mode sounds like the best solution for what I want it to do. I have to agree with John in wishing that there was a way to change the default gear, but I'll take the latch mode and learn to bump it with the throttle as necessary and go from there. Since we didn't travel in it this year (a trip to Ireland, then paying an extra $8,500 for our house roof replacement because of asbestos), I'm in hopes of getting a few more little things done before we go on vacation next year, and this sounds like a top priority for us.

[stuplich@ymail.com]

Thank you to Mel, Brett & John
I've wondered about being able to change the parameters of the pac brake (now that I have mine working) but wasn't sure what I wanted since I wasn't able to find a clear (to me) definition that other's have used. I think I'll be going over to my local Cat repair facility this winter and talking to their guru's and see how pricey it is - Latch mode sounds like the best solution for what I want it to do. I have to agree with John in wishing that there was a way to change the default gear, but I'll take the latch mode and learn to bump it with the throttle as necessary and go from there. Since we didn't travel in it this year (a trip to Ireland, then paying an extra $8,500 for our house roof replacement because of asbestos), I'm in hopes of getting a few more little things done before we go on vacation next year, and this sounds like a top priority for us.

05wingrider
I believe that the default gear can be electronically changed as well, however mine is set to 2nd (and I've had no problem with that on my now "150,000 mile" coach).

BTW because of how I use my Pacbrake my original disc brake pads lasted over 140,000 miles, with no damage to the rotors.

[wolfe10]

I believe that the default gear can be electronically changed as well, however mine is set to 2nd (and I've had no problem with that on my now "150,000 mile" coach).

BTW because of how I use my Pacbrake my original disc brake pads lasted over 140,000 miles, with no damage to the rotors.

Correct. An Allison dealer can change the pre-select gear to anything you want. No right/wrong answers. Best pre-selct gear for mountain driving is 5th. Best for coming to a stop is 2nd.

I have mine reset to 5th and use down arrows to choose lower gears. More choices for mountain driving, but more driver input needed.

Decide what works best for YOU.