Grade brake

[macantic]

Does anybody know how the "Grade Brake" works on a 2006 Pace Arrow 37C 8.1L engine workhorse chassis,it doesn't seem to do anything when I turn the switch on. I don't see anything attached to the exhaust like a "Jake Brake", does it work with the transmission somehow? or is it a "Dummy" switch. Thanks for any advise!

[harris155]

Described here...
http://www.irv2.com/forums/f125/prop...ke-168704.html

[gruelens]

Interesting article with good info. Am I to understand that it is OK to spin the 8.1L engine up to 5,200 rpm?

Personally, I try to avoid rpm over 3,000 under load and 3,500 when descending a hill. I have the grade brake, but until now manually shift the 6 speed Allison on steep ascents or descents. Guess I am conservative with my power plant and driveline. Disclaimer: I have all day and part of tomorrow to do any hill.

[edgray]

Originally Posted by macantic

Does anybody know how the "Grade Brake" works on a 2006 Pace Arrow 37C 8.1L engine workhorse chassis,it doesn't seem to do anything when I turn the switch on. I don't see anything attached to the exhaust like a "Jake Brake", does it work with the transmission somehow? or is it a "Dummy" switch. Thanks for any advise!

Assuming that Fleetwood hooked it up correctly, the TGB switch allows the feature to work as designed when in the "on" position. It is a feature that accomplishes the same thing as a manual downshift using the lever.......BUT, the TGB will not cause a DS unless the TCM senses what the engineers call Negative Slip at the torque converter. Negative slip occurs when coasting downhill, so the TGB won't "normally" cause a DS on flat road stops, or "most" stop & go driving. It is designed to require a GRADE.

To answer your first question, YES it works to cause the tranny to downshift when the brake pedal is depressed and certain other conditions (NS & RPMs) are met. IMO, they should not call it a TG BRAKE, because most people think of brakes as friction. TGB is intended to help the driver cause a DS without taking his eyes off the road to shift the lever manually.

Hopefully you'll notice yours working next time you are in hilly terrain and apply the brakes for a few seconds.
Ed

[wa8yxm]

I will describe how it works for me.

Grade brake on: I apply the SERVICE brakes, and if the RPMs are within range it will downshift.. When the RPM's get too high it will upshift so as to keep the pistons INSIDE the engine where they belong.

(Allison transmissions are rather smart when it comes to that kind of thing).

Sometimes a 2nd application of the brakes will cause a second downshift. Sometimes not.

What it does not do is "Try to hold your speed" It may do that but it mostly assists the service brakes, Makes me use them a whole lot less coming down the mountain.

Oh, to disengage, Tape the accelerator, the tranny will almost instantly upshift (less you have slowed down too far).

I have heard discussion claiming that using it is not good.

I remain not convinced of that however.. And thus can not argue the point, either way.

[UFO Pilot]

I have been using for for 52000 plus miles with no problems. It is always on.

[jeepfreak]

I leave it on all the time except for really long down grades. I to don't like the real high rpms. When it reaches 4000 on a down grade that's my max, then I will control it manually with the switch off. I don't like the trans possibly down shifting again when I have slow down even more using the brake pedal.

[Alan_Hepburn]

Originally Posted by jeepfreak

I leave it on all the time except for really long down grades. I to don't like the real high rpms. When it reaches 4000 on a down grade that's my max, then I will control it manually with the switch off. I don't like the trans possibly down shifting again when I have slow down even more using the brake pedal.

The transmission control module will not let a downshift occur if the result will be an over-rev situation. It's a pretty reliable system...

[gbs2320]

Originally Posted by gruelens

Interesting article with good info. Am I to understand that it is OK to spin the 8.1L engine up to 5,200 rpm?

Personally, I try to avoid rpm over 3,000 under load and 3,500 when descending a hill. I have the grade brake, but until now manually shift the 6 speed Allison on steep ascents or descents. Guess I am conservative with my power plant and driveline. Disclaimer: I have all day and part of tomorrow to do any hill.

I do the same as you. NO, NO, NO I never let mine go over 4,000 for more than a few seconds even with the grade brake no matter what that article says or implies. I use the brakes to slow it down enough to blip the throttle to get it to upshift and lower the rpms. Too many 8.1 have come apart from frequent use over 4,000 rpm IMHO from anecdotal stories on this forum alone. The power peak is below 4000 anyway and I wont let the grade brake take me into danger either. Greg

[Fred and Bonnie]

Originally Posted by gbs2320

The power peak is below 4000 anyway and I wont let the grade brake take me into danger either. Greg

Depends on the year.

The Specifications of an 8.1L Engine | eHow

Fred

[RBAYBE]

The brake will not operate when the transmission is in Overdrive.

[Alan_Hepburn]

Originally Posted by RBAYBE

The brake will not operate when the transmission is in Overdrive.

Then mine must not be working right - it will down-shift with moderate pressure on the brake pedal with no problem, and up-shift when the go-pedal is pressed. My overdrive switch has never been touched by me - I leave it in high overdrive all the time and let the transmission computer decide what gear is needed. Maybe you've got a different type of grade brake?

[JohnRR]

Originally Posted by RBAYBE

The brake will not operate when the transmission is in Overdrive.

My 06 works in overdrive as well.

[RBAYBE]

I have a 2005 Allegro Bay (since new) with a 1000 Allison and the exhaust brake never worked when I first got it. Couldn't figure it out......then I read the Allison Owners manual.....WOW, Quote: will not operated when in overdrive.??????? Has operated fine since.