Community Forums

BigDadThomas · 08-17-2005, 01:19 PM

My 2005 MH has the transmission braking feature. Or at least it did. Recently, when I flip the switch and hit the brakes, I don't sense it downshifting like I remember it did when we first got the rig. The switch works and the instrument light comes on.

Does anyone have a good test to confirm that this feature is working? I am thinking that I should start downshifting instead of waiting for this to engage.

Ideas?

BigDadThomas · 08-17-2005, 01:19 PM

My 2005 MH has the transmission braking feature. Or at least it did. Recently, when I flip the switch and hit the brakes, I don't sense it downshifting like I remember it did when we first got the rig. The switch works and the instrument light comes on.

Does anyone have a good test to confirm that this feature is working? I am thinking that I should start downshifting instead of waiting for this to engage.

Ideas?

Tom N · 08-18-2005, 06:40 AM

I assume you know that with the grade brake switch turned on the downshift occurs when you tap the brake pedal. Are you tapping the brake pedal??

rvr2352 · 08-18-2005, 02:12 PM

The Allision trans is bullet-proof because of it's computer controls. It will not allow us to hurt it by downshifting before all rpm and speed values are in tolerance. If you enable the grade brake and the coach has not slowed down to where the values are met, you just keep braking with the service brakes until the computer downshifts the trans. After that it will continue to seek a lower gear as it slows down unless you feed it fuel to accelerate. As you approach the crest of a grade it might be prudent to engage the grade brake before tipping over the top.
Steve

Scooter · 08-19-2005, 05:06 AM

Don't know if you have the Allison 1000 or 2000, but sometimes you have to either tap the brake hard 2 or more times or apply steady pressure for the grade braking to kick in.

Sometimes, if the "brain" reads that the accelerator is not fully disengaged it will not permit grade braking. Maybe a piece of carpet is keeping the accelerator from fully disengaging.

There is a re-flash available, if it comes to that.

You should visit http://www.dieselpage.com and/or the other website which name I forget but is very similar. (http://www.thedieselplace.com)

BigDadThomas · 08-23-2005, 01:26 PM

Thanks for the suggestions.

I took the motorhome for a trip of about 400 miles this past weekend, from Seattle to Long Beach, WA. Lots of hills.

At no time, could I ever succeed in getting the transmission to downshift. I would flip the switch for braking and then hit the brakes. Soft, hard, twice, it didn't seem to matter. Sure, once I got the thing slowed down enough, it would kick to a lower gear, but that's not how it worked when we first received the MH.

For most of the trip, I used the Overdrive On/Off switch for downhill braking, since that would at least give me "one" gear change.

Thus, I'm still looking for a solution. :-(

Rocky 2 · 08-24-2005, 04:47 AM

My dealer instructed me to turn on the Grade break, turn off the overdrive, and down shift manually in order to engage the grade breaking function. Frankly, this sounded strange to me. How do the rest of you work it?

2006 Southwind 32VS, W20

Teach · 08-24-2005, 06:38 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Rocky 2:
How do the rest of you work it? </div></BLOCKQUOTE>

I just flip the switch on and then when needed I tap the brake pedal and the transmission downshifts. If I need more I apply the brakes to slow down further and at the appointed rpm the tranny downshifts again. Works pretty slick.

max49 · 08-24-2005, 06:07 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Teach:
[QUOTE]Originally posted by Rocky 2:
How do the rest of you work it? </div></BLOCKQUOTE>

I just manualy downshift, plenty early too, here in Colorado

Fred and Bonnie · 08-26-2005, 05:18 PM

Like Teach, I leave the Grade Bake engaged all the time. The system has to sense a "pushing" condition to activate. Worked just great in Yellowstone and the Teton's, you just don't have to go looking for gears to downshift.

Fred

Brewer · 12-01-2005, 12:15 PM

I hate to say this, but I agree with BigDadThomas & Rocky 2!! The '05 W22 TGB is far from "bullet-proof". I too tried out the Grade Brake feature on my Dolphin before I bought it, and it worked Ok on a moderate hill, or on the level. Yesterday however, it got it's first real test, on the return trip from Joshua Tree NP. Just west of the town of Joshua Tree, the road ( Cal. 62 ) makes a quick drop from virtually level, to about a 6 & 1/2 percent grade. At the down-grade warning sign, I cut the OD & turned on the Grade-Brake switch. The speed stayed at 60 MPH, but the RPMs went from about 2200 to about 3000. At around 100 yards down the hill, I tapped the brake pedal and got no response ( MH picked up speed ). I pushed harder on the brake, but still no down-shift ( MPH down to 55 & RPMs down to about 2600 ). I would have expected the tranny to shift to 3rd, and the RPMs to rise to about 4000, but no dice!
I would especially like to hear from driVer, or the other WH experts on this forum, about "what to do next". I am an Electronics Engineer ( 30 years experience with Micro-Ps ), and do not subscribe to the phrase "bullet-proof". I went round-and-round with Ford on a similar issue 10 years ago, re their crappy E4OD tranny & associated ECM module. I am open to all suggestions as to "what to do next".

DriVer · 12-01-2005, 03:06 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Brewer:
I hate to say this, but I agree with BigDadThomas & Rocky 2!! The '05 W22 TGB is far from "bullet-proof"... I am open to all suggestions as to "what to do next". </div></BLOCKQUOTE>I just want to reiterate and support rvr2352's post.
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The Allison trans is bullet-proof because of it's computer controls. It will not allow us to hurt it by downshifting before all rpm and speed values are in tolerance. If you enable the grade brake and the coach has not slowed down to where the values are met, you just keep braking with the service brakes until the computer downshifts the trans. After that it will continue to seek a lower gear as it slows down unless you feed it fuel to accelerate. As you approach the crest of a grade it might be prudent to engage the grade brake before tipping over the top. </div></BLOCKQUOTE>Now at no time did anyone in this thread suggest that TGB is "bullet-proof" however the Allison transmission and it's computer systems are.

The computer systems just won't allow you to blow up either the engine or the transmission - it ain't gonna happen, it's bullet-proof.

The technique that needs to be employed in all operational modes it to assure that the motorhome is traveling at a speed that will allow the transmission to downshift. If you're going too fast you can manually down shift to "first gear" and nothing will happen. Once you scrub off enough speed the tranny will down shift and afford you compression braking. If you continue to over speed the engine the transmission will automatically up-shift regardless of gear selection and the operator will have to get on the brakes.

Once you find yourself needing to get on the brakes you need to pump the brakes in approx. 1 to 2 second intervals until you scrub off enough energy (speed).

When the TGB is used within it's operational parameters that are listed in the owner's manual, it's an effective system therfore the operation of the TGB needs to be reviewed and adhered to. It's a useful tool however it's only bullet-proof to a point.

Fred and Bonnie · 12-01-2005, 05:07 PM

Last summer in mountain driving conditions,I found the operating parameters as DriVer described. I tried to manually downshift when the GB didn't, no luck the drivetrain would have been operating out of limits. The solution was to apply the brakes and drop speed/RPM, the GB shifted down as advertised.

Fred

BigDadThomas · 12-05-2005, 10:01 AM

Here's an update to my original post. My TGB (transmission grade braking) is still broke. I've been to the certified Workhorse guys. Picked it up last Saturday. They didn't even try to work on it and said that I have to go to an Allison shop for TGB. In response to some of the other posts, my coach will not shift, no matter how many times I tap the brake or how slow the speed gets. I know the difference, because it did work for the first few months. We now have the rig back at the dealers for some other work as well as asking them to fix the TGB. I'll let you know how this turn's out. :-)