Community Forums

Barrier2 · 11-24-2009, 09:22 AM

Thanks EngineerMike. Where can I find details about that? Would I have to keep my foot on the brake or would the switch work... press brake on---Pac On press.. brake again--- Pac off?
I think I might be even more confused.
I would think a method to turn it on say in traffic (when entering a city) or on a downhill run. And then be able to turn it off for normal driving would work best. If it goes on and off whenever I hit the brake, for example when I want to shave off a few miles per hour in a down hill run it might cause more harm then good.
From what I now understand if I feel a need to activate the Pac Brake I have to keep my left foot on the floor pedal for it to activate and provide exhaust braking is that correct?
I may still not understand the full value and usage of the Pac Brake.
Barrier

rmmpe · 11-25-2009, 06:27 AM

Barrier,
As mentioned, I have an SPST switch that I can turn on & off by tipping the rocker. When on, unless using Cruise control, the downshift/Pac Brake actuates. However, to prevent engine over-speed, my unit will not go into this mode over 60 MPH.

Regardless, there are times when going over 60 MPH I want the Pac Brake to actuate but don't want the downshift to occur, like on a long downhill. In order to make this happen, I installed a manual override circuit (separate/dedicated momentary SPST switch and solenoid actuated air valve) to make the Pac Brake close, which allows me to use only the engine braking feature while in 6th gear. This circuit, with a parallel switch under the bed, also allows me to easily excercise the Pac Brake when lubricating it.

The entire circuit is fused and isolated from the original downshift/Pac Brake circuit so there is no possible feedback to the ECM or TCM.

All this may be somewhat confusing but it works to my satisfaction and gives me greater control over broader driving conditions.

Barrier2 · 11-26-2009, 12:40 PM

Hi RMMPE, Thank you for the response. I will be adding switches etc as soon as I can.
Happy and Healthy Thanksgiving to all Especially our Troops!
Barrier

rmmpe · 11-26-2009, 12:56 PM

Barrier,

I erred when I said I installed another solenoid valve. Actually, after looking at my schematics, it was a momentary switch around the normal circuit to manually actuate Pac brake and a relay to isolate the trans control module when manually overiding the normal circuit (don't want any feedback to that little jewel).

Regardless, thanks for the wishes, which are reciprocal.

Happy Thanksgiving to all.

God bless our troops and all who've served.

EngineerMike · 11-26-2009, 01:15 PM

Barrier- Brakeswitch is a completely parallel switch device. If you install it w/an on/off switch then Off disables it and On enables it; if no switch then it is on when you step on the brake pedal (it gets its signal from the brake light circuit) and off otherwise.

The beauty of this is actuating the PacBrake become automatic when you use the brake pedal. Some (I'm guessing a lot of folks) learn to engage the PacBrake alone by depressing the brake pedal only enough to get a brake light but not enough to use much if any service brake. If you find there are conditions where the addition of PacBrake to service brakes is a nuisance you can use the on/off switch to take it off line, then turn it back on say when in city traffic where you want all the safety factor on braking you have available. Makes brake actuation for setups like yours completely automatic w/only the normal brake pedal action.

rmmpe · 11-26-2009, 01:26 PM

True Mike.
But, it won't help at all if you're going too fast for the engine to safely downshift, will it?

EngineerMike · 11-26-2009, 02:42 PM

Bob- I paid that fine, and now would like to put the matter behind me.

rmmpe · 11-26-2009, 04:06 PM

Good Lord, Mike.

I didn't mean to dredge-up an unpleasant memory.

Mea Culpa, mea culpa, mea maxima culpa.

I had a problem with a front brake dragging this summer, was on a very long 5% grade and did not want to use the brakes until I was able to pull off to the side. Wow, I got up to almost 80, which is a lot faster than I like to go in the old beast. Having the trans unable to go into the downshift/Pac Brake mode over 60, I felt somewhat helpless, which is why I came up with the manual over-ride circuit. Using it in conjunction with 5th gear works pretty well.

Maybe not for everybody, I can now employ just the Pac Brake, which does help on long downhills.

Happy Thanksgiving (I just finished dinner and am wallowing around a bit).

J Walker · 11-30-2009, 11:14 AM

Barrier 2, I would replace the momentary switch with a SPST, or in other words one that turns on the exhaust brake when you switch it and turns it off when you switch it again. That is what I have, though it is a hand switch on the console on my left side. I also have a brake light on my dash when the exhaust brake actually engages, not just when the switch is on.

VERNL · 12-06-2009, 10:48 PM

In regards to the foot switch actuated exhaust brake, for what it is worth, I had a 96 Beaver Monterey with such a setup that I used for 11 years. The switch had to be held down to keep the exhaust brake working. The exhaust brake would not work if the cruise control was engaged. I found it a great help. In fact I used at every stop sign and I did not have to touch the brakes until about 20 mph. The transmission down shifted all the way to 2nd gear. This setting is an option in the software. The only thing I had to watch out for was letting the rpm drop down to the point of the next lower gear shift point when I only wanted to control the down hill speed. This was expecially critical when the tranny had shifted to 4th gear and I didn't want it to go to 3rd gear because of too drastic a slow down. It worked great all the time for a 100,000 miles.
VERNL