Grade brake activation?

[cannon man]

does the brakelight switch on the brake pedal activate the grade brake? if so how is the switch in the bracket adjusted? i see threads on the shaft but don't see how to adjust it. my problem is i have to push on the pedal as hard as i can to make it work. seems like it should be easier to do.
thanks, dave

[dieselclacker]

Dave, the switch screws in or out on the threads you are seeing, depending what adjustment is necessary. Sound like you may need to run the switch in a little closer to the pedal shaft. I do not have grade brake on my unit, but believe it is activated by brake light switch.

Dieselclacker

[DriVer]

Quote:

Originally Posted by cannon man my problem is i have to push on the pedal as hard as i can to make it work. seems like it should be easier to do. thanks, dave

cannon man, My grade brake is different than yours however I'm going to take an blind stab in the dark at what's going on in your case, OK?

The grade brake actually is applied and begins to work over time. This time is only a very few seconds. When you are stepping on the brake "hard" I believe that you are allocating the time that is required to activate the brake.

Therefore I believe that it's not so much a function of how hard you are pushing but how long. Does that make sense? Try pressing the brake pedal down less hard but stay on the pedal a few extra seconds to rule out my suggestion.

The grade brake is applied electronically. Have someone check your brake lights while you're parked. See if they come on right away when you step on the brake, if they do it's unlikely that the switch is the problem. If your cruise control disengages immediately when you tap the brake, again unlikely something is wrong with the switch adjustment.

I hope this helps you!

[RickNB]

I have found that some decrease in speed has to be seen from applying the brake before the down shift occurs just tapping the brake like you would to disengage the the cruise will not cause a down shift. Does that sound right?

Rick

[DriVer]

Quote:

Originally Posted by RickNB I have found that some decrease in speed has to be seen from applying the brake before the down shift occurs .... Does that sound right?

Rick, That's right. When you step on the brake and decrease the speed, that event takes place "over time". You see what I mean.

There are other processes that take place inside the transmission that pertain to drivetrain load etc. but that again takes a very few seconds to occur as well. There some "choice" language that goes on between the TCM and ECM and then the deal is negotiated.

In my experience with my GB I thought it was going to be a tap event trigger but it takes a little bit of application time to get the command to execute.

[wa8yxm]

Does the switch activate the grade brake: YES. also the ABS and the brake lights

if the ABS and Brake lights are working normally.. the switch is as well

I am currently a few yards off I-75 in the great state of Georgia

I came here via I-24 through Tenesee and I-65 in KY and TN before that

I can tell you the Allison Grade Brake... WAS FANTASTIC.

I flipped on the switch to enable it.. And when I headed down a 5% grade I braked down to around 57 MPH. it climbed up to 59 before I got to the bottom.. ON a six percent grade I had to break down about 4 times in six or seven miles.. Each time I took it from about 60MPH down to around 43-45 and let it climb back up till it up-shifted to protect the engine,, Then I'd break it back down

THat is far and away one of the best inventions ever put in an automobile.

[TrekPR]

I've found if I tap the brakes once then brake to the desired speed the grade brake downshifts to the necessary gear to hold that speed. If it doesn't down shift immediately I tap the brake once more. There is normally not much of a lag time to the down shift. The biggest trick is staying off the gas so I don't have to brake again at the next curve. Patience is difficult for some of us.

[DriVer]

Quote:

Originally Posted by TrekPR I've found if I tap the brakes once then brake to the desired speed the grade brake downshifts to the necessary gear to hold that speed. If it doesn't down shift immediately I tap the brake once more.

TrekPR, How long are one of your taps? A 1/4 second, 1/2 second or other?

I have not had to apply my brake for any more than 1 to 2 seconds to get the Grade Brake to activate.

[MotorhomeMan]

Quote:

Originally Posted by wa8yxm I flipped on the switch to enable it.. And when I headed down a 5% grade I braked down to around 57 MPH. it climbed up to 59 before I got to the bottom.. ON a six percent grade I had to brake down about 4 times in six or seven miles.. Each time I took it from about 60MPH down to around 43-45 and let it climb back up till it up-shifted to protect the engine, then I'd brake it back down

On a steep grade, even after the transmission downshifts to a lower gear, the motorhome will want to pick up speed. How high of an engine RPM do you allow before braking to reduce speed and engine RPM's? In your example above, (running up to 60 mph) were you in fourth or third gear when it ran back up to 60 mph?

[DriVer]

Quote:

Originally Posted by MotorhomeMan On a steep grade, even after the transmission downshifts to a lower gear, the motorhome will want to pick up speed. How high of an engine RPM do you allow before braking to reduce speed and engine RPM's?

MotorhomeMan, On a grade a driver should be able to anticipate how much grade brake function is required to descend as a sane speed.

When a downshift is completed and the vehicle is observed speeding up further, a second application of the brakes will be required and when it's safe to do so (RPM wise) the Allison will downshift again. You will have to be on the brake until the transmission downshifts. It doesn't take a long time to scrub off enough speed before the tranny will accept an additional downshift.

Regarding my GB, as soon as I get on the brake regardless of speed, I go to 4th. By anticipating what I am looking at and if I see the vehicle is moving too fast, I apply the brake again. This action will cause an additional downshift to 3rd. If I believe the grade and road conditions warrant slowing further, a 3rd application of force to the brake pedal will bring me down to 2nd gear. Removing my foot off the brake the vehicle will stay in 2nd until I step on the throttle. Under the right RPM and speed conditions my GB will downshift all the way to 1st if I let it.

I do not use cruise control conjointly with grade braking. I have seen RPM however around 4200 to 4400 and it does not concern me very much. As long as I am incrementally going slower on the grade the RPM will follow.

What is really neat about the UP Allison Grade Brake is that it follows normal driving routine without too much thinking. If you want to go slower, naturally a driver would step on the brake. What the GB does is follows that up by downshifting automatically in meeting that need. Now if you need to go slower, a driver would naturally step on the brake again and this will cause another automatic downshift. Want to speed up, just apply the throttle and this disengages the GB.

Unlike wa8xym, I leave my GB switch "ON" at all times. The GB system only works when it's supposed to. I never know it's there unless I need it.
.

[wa8yxm]

I often forget to turn mine off... A lot depends on where I"m driving.. THe planes (Long flat runs) I turn it off.. But even in Michigan we have hills steep enough to need it.

[DriVer]

Quote:

Originally Posted by wa8yxm I often forget to turn mine off... A lot depends on where I"m driving...

wa8yxm, In turning off your OE TGB, is that something you feel comfortable doing or is it in your opinion an operational need?

If you were previously driving an RDP with a Jake or Exhaust Brake, I could see it.

[dieselclacker]

Out west where I do most of my motorhoming, I try to keep the RPM of the engine around 4000 to 4200 while decending long grades under engine compression. If it goes above this range, a quick HARD stab on the brake pedal brings the RPM and speed back down to below this range, where I once again let the speed and RPM increase before repeating this procedure again. I find third gear in my Allison 5 speed trans if probably the most versatil gear for both climbing and descending long grades out here. Third gear in my 32 foot W-22 has no problem pulling its self and my toad up or down long 7% grades that are common here.

Dieselclacker

[TrekPR]

Driver, a tap is a tap but it isn't a second and the brakes are not actually applied. It is possible this is more of a habit and not really necessary, but I have had times when I had to apply the brakes a second time before the grade brake kicked in. Not a big deal I have always thought it normal.