Grade Brake

[jlazar]

I have a 37ft Allegro Bay (W24, Chevy 8.1L, Allison 1000).  I am towing a CRV with an M&G braking system installed.  There is a button on the dash labeled Grade Brake.  I have pushed it in a few instances when going down a steep grade.  But I am not sure I am using it properly.  Could someone please explain how a grade brake works.  Is it a function of the chassis, engine or transmission?  When is the proper time to turn it on?  And off.  What is the proper use of the brake pedal in conjunction with the grade brake?  All inputs and advice appreciated.  I will be making my first trip through some hilly terrain (Nevada/California) this spring.

 

[John From Detroit]

The grade brake on an Allison transmission is a multi-control activated device.

First turn it on and consider leaving it on.. This will not harm performance or millage.  In fact, in normal driving the thing operates in "Standby" mode (does nothing save monitor the other switch,, that switch is the brake pedal switch, same one that turns on the brake lights).

To engage the grade brake, Depress the regular (What I call Service) brakes. Slow a bit, you will hear the engine kick up in speed, THIS is the grade brake cutting in, normally it would not do that till it gets down very slow.

To cancel grade brake when you get to the bottom of the grade.. Press the accelerator pedal. (or resume cruse control) or turn it off, but frankly, no need to do that.

NOW: Some folks seem to feel using the grade brake will put additional wear and stress on the tranny and lead to early transmission failure.. I'm not one of them.. but I pass on that bit simply because I read a lot and that includes their posts in other forums.

But the grade brake does not engage till you use the regular brakes, It also will not engage if you are going too fast (No need to spread pistons all over the country side)

Though I think my Allison needs a bit of a computer flash.. That dang thing is smarter than I am. It works well to protect the engine while using engine braking to slow the vehicle on hills.

NOTE: in normal flat land driving, use of the grade brake means it downshifts very quickly, thus adding engine braking to the brake mix and reducing wear and tear on the service brakes.

But it only works when you press the main brake pedal for a bit, Just how long I don't know, Sometimes I have to press two times to get it to engage.  I have seen it downshift 2 gears here in SC on a few hills I'll be going down tomorrow.

 

[jlazar]

Forgot to mention that I also have an O/D off switch.  Is that used primarily for climbing?  Or down steep slopes also?

 

[Gary RV_Wizard]

You can leave OD on and the grade brake too. There is very little reason to ever turn either of them off - they nearly always do the right thing under automatic control.

You would turn the OD off if cruising on rolling hills and the transmission "hunts", i.e. is rapidly switching in and out of the overdrive gear.  Might want to turn the Grade Brake off in a similar scenario - it is engaging too often when the hills really aren't steep and you want to coast down them without slowing.  But if you aren't noticing any negative effects of either one, leave them both on.

 

[Oscar Mike]

You can leave OD on and the grade brake too. There is very little reason to ever turn either of them off - they nearly always do the right thing under automatic control.

You would turn the OD off if cruising on rolling hills and the transmission "hunts", i.e. is rapidly switching in and out of the overdrive gear.  Might want to turn the Grade Brake off in a similar scenario - it is engaging too often when the hills really aren't steep and you want to coast down them without slowing.  But if you aren't noticing any negative effects of either one, leave them both on.

Would the same be applicable to the Tow/Haul function on Ford?

 

[Gary RV_Wizard]

I think so, but maybe a Ford owner can comment better.

 

[jlazar]

Thanks for the clarification and guidance.

 

[kenb1023]

Would the same be applicable to the Tow/Haul function on Ford?

Yes, the transmission down shifts faster when you hit the brakes in the Tow/Haul mode.  Helps a bunch going down hill.

 

[jlazar]

Drove from Reno to Sacramento today.  My first time traveling through terrain with numerous downhills (5-6% grade).  Used the grade brake as you guys advised.  Very impressed with how it performed.  Once it engaged, on the entire trip I only hit the brake pedal 2-3 times while going downhill.  Saw several trucks with smoking brakes.