I have a 03 2500HD with the duramax and allison trany. I tow a 30ft 5th wheel that weighs right at 10k ready to go. I love the performance going up hill and the fuel economey is great,but, havent really figured out how to go down hill and not have the tach go into the red.I do not have it in overdrive and I have the haul mode on.Is the exhaust brake the answer? If so Ive heard the the banks system is the best match for the allison. They are not cheap.Anyone else out there with the same experience?:help:

murphone..
Dont sweat it, that's the way its designed to run! If the RPMs get too high, this smart truck will up shift for you. If it bothers you too much, just gently ride the brakes till you get slowed down and let the Dmax/Ally handle the load. I have pulling about 50% more than you for a few years now and I have had no problems. After all my towing, I would not have anything else.

Before installing the exhaust brake going over the mountains, it was a scary feeling. Now with the exhaust brake, I get to travel all over this beautiful Country and don't care what the grade is of the up coming hill. At all times, the entire rig is in complete control. Before the exhaust brake, it felt like the rig could easily go out of control. Safety is number one.

If you don't go on graded hills often then don't worry about it. Mitchagain is correct that the truck is smart and hopefully will take care of you. BUT...All you need is one brake problem on the truck or trailer and suddenly you are in BIG trouble.

BD Brake is easy to install and easy to use.

Have read the replies and I thank you for the info. I also read bpzlv first tow and the replies he got from people and it sounds like unless Im going to do some serious hill traveling its not a big problem just dont let the tach linger in the solid red area very long. Have also done some reading about the different exhaust brakes out their and found that area very informative. This is a great site,can you tell Im a new user.

Hey murphone,

My first time in the mountains was in Kenworth T300 (aka Baby KW) that weighed about 38,000. At first, I was really cautious and used the Jake brake as much as possible and tried to keep the speeds well under the limit. After a couple thousand miles, I learned that the faster you go, the more the air pushes back and keeps you from gaining more speed. For instance, instead of taking a downhill at maybe 45, go 55 or 60 if it's fairly straight. You can let the Jake brake and the wind do more work, and give your brakes a break (har har).

You can't do this on all roads, and I'm not saying you should. But after I got more comfortable, and was on a wide and fairly straight part of interstate, I was much more relaxed when I wasn't using the brakes every 10 seconds or so. In short, I just added about 10 mph or so, and was still safe, just using less brakes to keep my speed constant. In this case, I was more nervous going at 45, than I was at 55.

I hope that all made sense.

but, havent really figured out how to go down hill and not have the tach go into the red.
Which red line are you concerned about? The cross-hatched 3200 - 4800 RPM or the 4800 RPM and above? The cross-hatched section is the normal range for grade braking. It may sound like you are revving too fast but that is the way the engine was designed to work. Most of the noise is from that big cooling fan beating the air to a pulp. If you try to add any power in this RPM range, the truck will upshift and lower the RPM back into the power range. If you were gaining speed and hit the 4800 RPM never exceed red line, the truck will also upshift to protect the engine. It simply will not allow you to hurt the truck. I pull 21,000 pounds GCW and can go down 6-7 % grades at 55mph and never touch the brakes after engaging the grade brake. 8-9 % will need some additional braking to keep the speed from climbing. At 10 % or above, I need to slow to 45 and drop one more gear to keep things happy. You can manage the loads without having to use an exhaust brake. Take a close look at the tach and the two redlines then hook up the trailer and head for the hills. After a little practice, you won't worry about downhills.

What Dave said.


:exactly: :exactly: :exactly:

Idahofox

Thanks Dave your response really makes me feel better. I just need to get away from this desk and head for the hills for a little practice,I guess I should read the manuel better.Thanks again I feel better

Your owners manual spells it out for you, these guys are correct in that the grade braking is designed to work well into the red zone.

After reading this thread, a question sticks out in my mind. How do we really know that "it's ok" to run downhill in the 3200-4800 rpm range??? I've seen it posted on this and other forums, but is it truly factual info or are we just passing along what other people have said (which makes it only hearsay and opinion)? I can't find anything in my owner's manual that talks about it - what section is it in?

I can believe that the engine or tranny won't explode if we do it just once or twice, but if we did it repeatably are we asking for trouble or premature wearout? I'd feel better if that section of the tach was yellow and not red. To me red means don't go there.

I'm not doubting or challenging, just trying to understand

If you question/do not understand the research thats been done, Do Your Own research.

These people have forgot more about the DMax than you will ever know.

Idahofox

The owners manual doesn't tell you much. The best source is from Allison. GM did write a tech bulletin so the service managers could explain it to their customers. JK did a good summery some time ago on his web page. http://www.kennedydiesel.com/allison_grade_braking.html

Hey murphone,

My first time in the mountains was in Kenworth T300 (aka Baby KW) that weighed about 38,000. At first, I was really cautious and used the Jake brake as much as possible and tried to keep the speeds well under the limit. After a couple thousand miles, I learned that the faster you go, the more the air pushes back and keeps you from gaining more speed. For instance, instead of taking a downhill at maybe 45, go 55 or 60 if it's fairly straight. You can let the Jake brake and the wind do more work, and give your brakes a break (har har).

You can't do this on all roads, and I'm not saying you should. But after I got more comfortable, and was on a wide and fairly straight part of interstate, I was much more relaxed when I wasn't using the brakes every 10 seconds or so. In short, I just added about 10 mph or so, and was still safe, just using less brakes to keep my speed constant. In this case, I was more nervous going at 45, than I was at 55.

I hope that all made sense.

If your not familiar w/ the Jake brake set up, the max braking power is at max rpm.

The new trucks w/ big hp motors cruise @ 1400 rpm but u don't have much engine braking @ that low rpm, so drop a couple of gears and don't worry about needing the brakes.

Look at the boost guage when the jake is on and the higher the rpm the more boost/resistance.

Look in your manual, I believe it is there. There also is a grade breaking article, I think from GM, floating around somewhere that talks about this. I have on numerous occasions let mine sit in 3800-4200 range for a couple miles.

Ok, I don't have the allison, but on my 6 spd can I downshift into the crosshatched red and do the same thing manually, not letting it go into the full red???? Is it safe for the engine???

Since GM set it up I'm sure it was tested a lot.

It looks like there’s not much knowledge or experience here about the safety of repeatedly going into the shaded red zone – up to 4800 rpm. Opinions yes, plus a stupid wisecrack. My 2002 Chevy Owner’s Manual (pg 2-97) does say ”Damage to your engine or vehicle caused by operating the engine in the red area isn’t covered by your vehicle warranty. Don’t operate the engine in the shaded red area.” This seems pretty clear, but then their Grade Braking feature automatically puts it up there. Allison says it is ok to operate in the dashed red zone, but then they don’t sell or warranty the engine.

So we have conflicting info on going into the red, and none of it addresses going up there repeatedly. It seems to me we’re left to our own judgment and comfort level. Much depends on how often, how long – a ¼ mile hill or a 5 mile mountain pass – and how high an rpm. Personally, I have no more faith that GM tested long term operation up there than I believe they did much real-life long term testing of the fuel injectors.

rightstuff,

Were you realy Born in the year 1992 ?

(2005 - 1992 = 13). My 2002 Chevy Owner’s Manual (pg 2-97).........?

Idahofox

Idahofox, what’s your problem? You have contributed nothing here other than bashing a person you don’t know and know nothing about. The Diesel Place deserves better. Maybe you don’t like me asking for knowledge, or you don’t like my writing style, or whatever.

Maybe you don’t understand the difference between knowledge and opinion. On long-term running in the red zone, real knowledge would have testing or experience behind it. Opinion doesn’t have such a basis. Since no testing or experience has surfaced, it looks like opinions (mine, yours, and everyone’s) are just speculation. I’m looking for more. Real experts do more than just speculate. OK?

Idahofox, what’s your problem? You have contributed nothing here other than bashing a person you don’t know and know nothing about. The Diesel Place deserves better. Maybe you don’t like me asking for knowledge, or you don’t like my writing style, or whatever.

Maybe you don’t understand the difference between knowledge and opinion. On long-term running in the red zone, real knowledge would have testing or experience behind it. Opinion doesn’t have such a basis. Since no testing or experience has surfaced, it looks like opinions (mine, yours, and everyone’s) are just speculation. I’m looking for more. Real experts do more than just speculate. OK?

You are the only proplem I have right now, what have your contributions to this thread been. Your not being bashed, your being spanked.

Sincere questions have been asked in this thread, and answered.



Q. Engine Speed - What is an acceptable engine speed after a preselect or grade braking downshift?

A. The TCM is programmed to command downshifts only when the resulting increase in engine speed will not exceed factory-set limits. Specifically: For the LB7 and LLY diesel engines: Maximum engine speed immediately following a preselect or grade braking downshift can be as high as 4,000 RPM. After a grade braking downshift, if vehicle speed continues to increase, an upshift will occur at 4,800 RPM engine speed.



Check Allison's Opinion Here (http://www.allisontransmission.com/service/faq/index.jsp?CategoryID=11#82)

I'm trying to be patient, but please do your own homework from now on.

Idahofox

Thank you for posting the Allison FAQ that I had referenced in my June 7 post. Go back and read it carefully. Also notice the Chevrolet quote that says - Don’t go up there, and if you do your warranty isn’t valid. Face it, there are no experts on repeated running in the red. Only opinion/speculation.

Sorry, everyone, that you’ve had to put up with this. I’m out of here. Adios.

Post your Source Documents if you want anyone to pay attention to you !

Idahofox

Warranty coverage is only limited if the dealer knows of something you did 'wrong.' Find someone that has it in writing that they blew their DMax grade braking in the hatched red and had the dealer decline warranty for running in the redline.

I've found thast in really serious grades truckers must pull over, stop, and shift into a lowers gear. I was on a mountain grade where the top speed was 35mph. I started down slow, and the allison kept me at 35 or lower almost all of the way down. I think some people get into trouble when they strat down too fast.

I've found thast in really serious grades truckers must pull over, stop, and shift into a lowers gear. I was on a mountain grade where the top speed was 35mph. I started down slow, and the allison kept me at 35 or lower almost all of the way down. I think some people get into trouble when they strat down too fast.

If you have to "Pull Over and Stop" to grab a lower gear, you would NOT be driving any of my trucks. :badidea:

Idahofox

Rightstuff

GM is talking about not going into that range by moding the engine and allowing it to operate in that range. If they designed it operate there during grade breaking, which they did, then they cannot deny warranty repair. For some reason many people think the factory engineers and warranty folks are stupid. They maynot be what everybody thinks is right but the manufacturers thoroughly test their products before producing them. It would be plain stupid not to do so. (I do wonder about Ford however.) They also continue testing after production to improve the product.

Bell Helicopter, whom I worked for, is still testing parts on helicopters that have been in product for many years. It protects manufacturers from lawsuits which everyone seems to think is their way to get rich these days.

Like someone said earlier. There is a lot of knowledge and research compiled on this and other websites. If it was a problem it would definitely be posted. That is what makes the internet and these websites so valuable. It helps to keep the manufacuters and dealers honest and keeps us informed.

My 2 cents.

Tom Cobb

To help you slow down going down hill, you might try just manually applying the trailer brake by hand using the controller. Let the trailer slow you down without applying the truck brakes. Works for me.

...I just need to get away from this desk and head for the hills for a little practice...

:exactly:

Now your getting the idea! We all need to get out more to the hills or the race track!

Papa

To help you slow down going down hill, you might try just manually applying the trailer brake by hand using the controller. Let the trailer slow you down without applying the truck brakes. Works for me.

Why pay for new brake pads on the trailer when you have a 'free' engine/transmission brake that doesn't heat up or wear out? Trailer brakes are cheaper than the truck though.

Let it go into the red and let it operate like its made to do. I see no need for exhaust brake for D/A works great without them.