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Old 02-02-2025, 10:54 AM   #1
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Allison grade brake

I looked but haven’t found anything on this subject so.
I understood that all Allison 1000 transmissions are actually fitted with the grade brake and it was an upgrade from the RV manufacturer to complete it by including a switch to activate it. Is this factual? I live in the mountains so every trip out and return home will have me climbing or descending. This would be a great upgrade I’m thinking.
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Old 02-02-2025, 11:09 AM   #2
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Are you looking at gas or Diesel? I am not aware of the 1000's having retarders. Those are even rare in the 3000 and 4000 series with most using exhaust or engine braking.
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Old 02-02-2025, 11:46 AM   #3
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Quote:
Originally Posted by Stude View Post
I looked but haven’t found anything on this subject so.
I understood that all Allison 1000 transmissions are actually fitted with the grade brake and it was an upgrade from the RV manufacturer to complete it by including a switch to activate it. Is this factual? I live in the mountains so every trip out and return home will have me climbing or descending. This would be a great upgrade I’m thinking.

the grade brake is a controlled downshift that keeps the engine from over rev.
when the switch is turned on the "brake" is controlled by the brake pedal.
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Old 02-02-2025, 11:48 AM   #4
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Quote:
Originally Posted by d23haynes57 View Post
Are you looking at gas or Diesel? I am not aware of the 1000's having retarders. Those are even rare in the 3000 and 4000 series with most using exhaust or engine braking.
grade brake is used on the workhorse 8.1 chassis, not sure which models
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Old 02-02-2025, 08:40 PM   #5
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Quote:
Originally Posted by Stude View Post
I looked but haven’t found anything on this subject so.
I understood that all Allison 1000 transmissions are actually fitted with the grade brake and it was an upgrade from the RV manufacturer to complete it by including a switch to activate it. Is this factual? I live in the mountains so every trip out and return home will have me climbing or descending. This would be a great upgrade I’m thinking.
Workhorse added the Transmission Grade Brake (TGB) feature beginning with either the 2005 or 2006 model year (not sure which). It was included on all their 8.1L gassers with an Allison tranny, either 1000 or 2000 series.

They included an off/on switch, which allowed the driver to decide IF he wanted it to activate or not. When on, the TGB feature would cause a 1 gear downshift upon touching the brake pedal, (subject to the ECM and the TCM agreeing that the DS would not over-rev the engine). I believe it also required the TCM to be seeing a "negative slip" condition, which indicates it isn't under power and is "coasting" downhill.

The TGB feature was basically a convenience / safety feature because the driver did not need take his eyes off the road to watch which gear he was selecting when downshifting using the column mounted shift lever. I believe a second application of the brakes would cause another 1 gear DS, (again assuming the ECM/TCM approved) .

IMO, the reason the TGB could be turned OFF was because it could be quite annoying with unnecessary downshifts when driving in stop and go traffic
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Old 02-03-2025, 08:52 AM   #6
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Thanks for all the insight. This is a 2004 Fleetwood Southwind 8.1 with the Allison. I had driven a 2008 national Seabreeze several months ago that had the feature and in town. I thought it was odd that it kept down shifting as an approach the lights and it was probably me having the brake . I was not familiar with a grade brake at the time.
I thought there was actually something wrong with the seabreeze transmission because of the way it kept on shifting in the owner didn’t have an explanation of why it was doing it. I assume he always drove around with that switch on.
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Old 02-03-2025, 09:55 AM   #7
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I have a W24 built in 2004 and it does not have that feature. Can it be reprogrammed? I am assuming most likely not.
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Old 02-03-2025, 11:25 AM   #8
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My 2005 Safari Trek, W20 chassis, Alison 1000 5 speed, operates as described below and will also downshift again if brakes applied at a lower speed. This can be bothersome if you controlling downhill speed by downshifting with the grade brake and also occasional momentary brake use. If you brake and slow down too much, the second downshift really revs the engine when all you wanted was a just touch of the brakes.

Another feature I discovered is that it doesn't shift into 5th gear on level terrain when the grade brake is ON. This happened last year and I almost panicked and thought there was a transmission problem until I realized the Garmin GPS had hit the Grade Break switch when it fell off of its mount

Quote:
Originally Posted by edgray View Post
Workhorse added the Transmission Grade Brake (TGB) feature beginning with either the 2005 or 2006 model year (not sure which). It was included on all their 8.1L gassers with an Allison tranny, either 1000 or 2000 series.

They included an off/on switch, which allowed the driver to decide IF he wanted it to activate or not. When on, the TGB feature would cause a 1 gear downshift upon touching the brake pedal, (subject to the ECM and the TCM agreeing that the DS would not over-rev the engine). I believe it also required the TCM to be seeing a "negative slip" condition, which indicates it isn't under power and is "coasting" downhill.

The TGB feature was basically a convenience / safety feature because the driver did not need take his eyes off the road to watch which gear he was selecting when downshifting using the column mounted shift lever. I believe a second application of the brakes would cause another 1 gear DS, (again assuming the ECM/TCM approved) .

IMO, the reason the TGB could be turned OFF was because it could be quite annoying with unnecessary downshifts when driving in stop and go traffic
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Old 02-03-2025, 02:39 PM   #9
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Quote:
Originally Posted by David 70 View Post
I have a W24 built in 2004 and it does not have that feature. Can it be reprogrammed? I am assuming most likely not.
I found that it was first available on 2005 model year chassis.

Look up in the stickies at the top of this forum for a thread DriVer created when he installed the URVP aftermarket kit on his 2004W-22
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Old 02-03-2025, 02:43 PM   #10
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Quote:
Originally Posted by George Schweikle View Post
My 2005 Safari Trek, W20 chassis, Alison 1000 5 speed, operates as described below and will also downshift again if brakes applied at a lower speed. This can be bothersome if you controlling downhill speed by downshifting with the grade brake and also occasional momentary brake use. If you brake and slow down too much, the second downshift really revs the engine when all you wanted was a just touch of the brakes.

Another feature I discovered is that it doesn't shift into 5th gear on level terrain when the grade brake is ON. This happened last year and I almost panicked and thought there was a transmission problem until I realized the Garmin GPS had hit the Grade Break switch when it fell off of its mount
George: are you sure it wasn't the O/D switch that had gear 5 locked out? I believe the TGB feature "releases" upon return of throttle pressure.
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Old 02-03-2025, 03:21 PM   #11
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Stude,
My '04 Pace Arrow 37c has the 8.1 and the Allison 1000 combo, and the only brake I have is a switch to lock out 5th gear. Not a real grade brake but it works on some of the milder hills. However, Monarch Pass is NOT one of them.

Mike in Colorado
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Old 02-03-2025, 04:51 PM   #12
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Ed, so much for my memory. The OD OFF switch is right next to the GRADE BRAKE switch so that must have been the culprit. I remember hearing a higher than normal engine RPM in cruise speed, later fumbling with a switch, and off is when the upper part of the big rocker switch is pushed in. Its hard to believe a Garmin GPS could fall in such a way to affect a switch, but the 8 in. version is pretty heavy and the dashboard has some slope.

While driving downhill with the grade brake in its second downshift after additional braking, I don't remember achieving an up-shift without turning grade brake off but maybe was reluctant to apply even more throttle pressure to a racing engine. We don't drive in many hills needing the grade brake, but now I have to find a suitable road for experimentation.

Quote:
Originally Posted by edgray View Post
George: are you sure it wasn't the O/D switch that had gear 5 locked out? I believe the TGB feature "releases" upon return of throttle pressure.
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Old 02-04-2025, 08:50 AM   #13
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Ultra RV offers a grade brake modification for 2001 to 2003 W series chassis with the Allison 1000 transmission.

Click on ULTR RV GRADE BRAKE. I'm sure it works great.

I have a 2003 W20, I live in Colorado and tow a Jeep Cherokee behind my motorhome. Almost all my trips have a >9000' pass in them. Most a lot higher than that. I have no problems doing my own shifting to use the 8.1L engine as a brake on downgrades. I've traveled most mountain roads in Colorado without issue.

I70 tunnels
Vail Pass
Berthoud Pass
McClure Pass
Douglas Pass
Monarch Pass
Blue Mesa
Cerro Summit
Red Mountain Pass
Cochetopa North Pass
Fremont Pass
Tennessee Pass and Battle Mountain
Hoosier Pass
Raton Pass
La Veta Pass

To name a few I've driven on. That is not counting the Wyoming and New Mexico passes. The grade brake may be nice but manually shifting gets you there too!

Do you need a grade brake? Nope! Would it be nice...maybe!
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Old 02-04-2025, 09:11 AM   #14
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After reading how it works, I will stay with downshifting manually, especially for the cost. I live in SW MN, and we have no real hills that would need it anyway. I was out to Custer SD a couple of years ago and I had the P32 and I just shifted it manually and it worked fine.
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