Community Forums

mrjimbo · 07-05-2012, 09:16 AM

I have a 1998 National Tradwinds equipped with a 3126 300HP Cat, Allison 6 speed tranny, and Jacobs Exhaust Brake.

Currently, when the exhaust break is armed "switch on" and you are in 2nd gear or above and lift your foot all the way off the accelerator pedal, the transmission will shift down "eventually to 2nd" and the exhaust break will engage.

Since I lift my foot off the accelerator and coast down most small grades, I often do not desire to have exhaust braking, so I usually manually control the exhaust brake using the arm switch. I would rather be able to leave my exhaust brake armed and not have it engage until you hit the brake pedal and quit braking when you hit the accelerator pedal.

Is this possible with my Jacobs exhaust brake on my rig?

1ciderdog · 07-05-2012, 10:34 AM

I think this thread is about what your are looking for: http://www.irv2.com/forums/f26/anyon...me-110108.html
This is the website for that product: Brakeswitch, A better way to manage your diesel exhaust brake
I believe you can have Allison program the transmission to a mode that will do the same or similar.
I have the brake switch and use it all the time. I think it's a great device and makes hill country type traveling much more pleasant for the driver.

michelb · 07-05-2012, 11:35 AM

I didn't read the links above but I believe Allison service centers can reprogram the transmission so that it switches to 4th gear instead of 2nd when you lift.

dons2346 · 07-05-2012, 12:01 PM

I just keep light pressure on the throttle.

Old Trucker · 07-05-2012, 02:49 PM

Quote:

Originally Posted by mrjimbo

I have a 1998 National Tradwinds equipped with a 3126 300HP Cat, Allison 6 speed tranny, and Jacobs Exhaust Brake.

Currently, when the exhaust break is armed "switch on" and you are in 2nd gear or above and lift your foot all the way off the accelerator pedal, the transmission will shift down "eventually to 2nd" and the exhaust break will engage.

Since I lift my foot off the accelerator and coast down most small grades, I often do not desire to have exhaust braking, so I usually manually control the exhaust brake using the arm switch. I would rather be able to leave my exhaust brake armed and not have it engage until you hit the brake pedal and quit braking when you hit the accelerator pedal.

Is this possible with my Jacobs exhaust brake on my rig?

Hi mrjimbo, I am a retired cross country trucker. If you have a Jacobs("Jake Brake") You will have a two position, hi and low switch. This brake holds the engine valves shut. The other system is a Pac Brake, which is a damper that restricts the exhaust. This brake only has an on and off position. I would rather think you have a Pac Brake. Maybe the trans codes can be changed, I am not sure. I have a Pac Brake, it does the same as yours. I just control it manualy. If the switch is on.. it is designed to engage with the reduction of pedal pressure, It down shifts to increase the engine RPM's, therefore creating more exhaust pressure necessary for deceleration. Your brake is doing all it is designed to do. Yes I understand that you do not always want it to down shift, but I would save the trouble and run it manualy. best wishes, old trucker

Mr_D · 07-05-2012, 02:56 PM

Quote:

Originally Posted by michelb

I didn't read the links above but I believe Allison service centers can reprogram the transmission so that it switches to 4th gear instead of 2nd when you lift.

Yes, they can. Had it done to our 2000 DSDP, hated it ever after. Changed it by trading it for a new 2002 DSDP.

Mr_D · 07-05-2012, 02:58 PM

Quote:

Originally Posted by Old Trucker

Hi mrjimbo, I am a retired cross country trucker. If you have a Jacobs("Jake Brake") You will have a two position, hi and low switch. This brake holds the engine valves shut. The other system is a Pac Brake, which is a damper that restricts the exhaust. This brake only has an on and off position. I would rather think you have a Pac Brake. Maybe the trans codes can be changed, I am not sure. I have a Pac Brake, it does the same as yours. I just control it manualy. If the switch is on.. it is designed to engage with the reduction of pedal pressure, It down shifts to increase the engine RPM's, therefore creating more exhaust pressure necessary for deceleration. Your brake is doing all it is designed to do. Yes I understand that you do not always want it to down shift, but I would save the trouble and run it manualy. best wishes, old trucker

Jacobs makes an exhaust brake and some refer to it as a jake brake because of the manufacturers name, not how it functions.

R2Home · 07-05-2012, 03:07 PM

When I had my transmission serviced I had asked about re-programing the engine braking. They hooked a computor to it and changed the settings and had me try it out. I did not like the new settings so I had them change it back to what it was. As has already been said, I just keep a slight pressure on the throttle.

Triker56 · 07-05-2012, 03:17 PM

When you turn the exhaust bake on and the shift panel then says 2nd. That is the selected gear it will work down too. It doesn't automatic go to that gear right away. It may be in 5th when turned on and will work its way down to 2nd when the engine RPM speed & Allison talk to each other and say it is OK to move to 4th, then 3rd etc. Like others said, a slight pressure on the go pedal will turn the exhaust off, until you take the pressure off and it will return to exhaust braking.

mrjimbo · 07-05-2012, 05:18 PM

Yes mine is indeed a Jacobs brand EXHAUST brake. It does choose 2nd gear when it's on and I remove my foot from the accelerator pedal at speed.

I really like the exhaust break and it works REALLY well, sometimes too well. I just would like to leave it activated and not have it engage until I hit the brakes. The rest of how it works is fine.

I will look into the brake switch mod listed in the link above, but it's not a big deal to use it as is.

I had a close call with a person pulling out in front of me shortly after purchasing and needed all the braking I could get. After barely stopping in time to avoid smashing into the side of them, I realized it would have been nice if the exhaust break would have been active. I didn't think to flip the switch.

firedoc · 07-05-2012, 06:57 PM

Just have Allison reprogram your transmission. It will operate just as you described you wanted.

Gary RVRoamer · 07-05-2012, 07:18 PM

The CAT ECM can be re-programmed to engage the exhaust brake in the way you wish. Any Cat dealer should be able to help. Tell him you do not want the exhaust brake to latch when the throttle lifts and that it should be controlled by the brake pedal.

Pusherman · 07-09-2012, 05:46 PM

Quote:

Originally Posted by Gary RVRoamer

The CAT ECM can be re-programmed to engage the exhaust brake in the way you wish. Any Cat dealer should be able to help. Tell him you do not want the exhaust brake to latch when the throttle lifts and that it should be controlled by the brake pedal.

That's what I did. It's called 'Latch' mode.

And then go to Allison and have the shift point changed to '4' instead of '2' when the engine/exhaust brake is engaged.

With the combination of those 2 program changes above, it's really sweet to drive. I keep my exhaust brake on all the time.