Chevy 3500 HD exhaust brake question

[Garypowell]

Simply put the question is how do I know my exhaust brake is working?

I push the button on the dash, it lights up. The DIC says that "Diesel Brake is Engaged". But I can tell no difference between having it on and just using Tow Mode when stopping/slowing down. My transmission downshifts like crazy in either mode (and various combinations). I thought I was getting an exhaust brake not a transmission downshifting brake.

I assumed that I would not hear the BLAM, BLAM, BLAM....like the big rigs....but I hear nothing and as stated above feel nothing......so what am I missing here?

In Florida I could not tell any difference and thought.....well....I'm in Florida. Now out in Wyoming and Utah I am seeing some 6 - 8 - 10% grades. On the way down the grades have played with various combinations.....and see no difference in braking between tow mode and when the exhaust brake is turned on.

Thanks!

 

[falk1rk]

From what I have read it works in conjunction with cruise control. You set the speed you want to maintain and the system will take care of the rest. I have a 2004 so I have not done it myself but that is what I have read on the diesel forums and seen them use this technique on the performance head to head competitions. I am sure someone else here that actually has the same truck as you will chime in with real experience.

I also have read that the engine brake is gained from the variable vane turbo causing the back pressure, I think that is how all the new trucks work but I could be wrong.

 

[Doublegranch]

The exhaust brake should work in all modes not just cruise control....If you have the EB on and tow haul off and even the cruise control off you should have a very noticeable slowing in speed and in my Ram I do get the Roar of the back pressure! Not like the big rigs but it is very distinctive. Not sure on your truck but the Ram has three setting...off, EB on full and EB on auto...with it on full it will come on when you let up on the accelerator or hit the brake! When on auto and you let up on the accelerator without touching the brake you will free wheel and it will not come on....once you hit the brake it should go on full.
Not meaning to compare this with the Ram but that is all I know and experienced as Ram's are the only trucks I have owned.
Towing my new Sundance back from Elkhart in June with the EB always on full and the tow haul on...wow they worked with each other so well, I rarely had to use my brakes. If fact I didn't even know the Sundance brakes were not engaging until I returned home and did a test! Hope this helps.

 

[Piperflyer]

I definitely can feel it and hear it when I have it selected on my 3500 HD. Really keeps me slowed down without using the brakes on those 7-10% grades

 

[kkamshop]

If I read my manual properly and if memory serves me correctly it has to be in tow-haul for the exhaust brake to function.

 

[Doublegranch]

If so, that would pertain for the GMC/Chevy product only!
Not so for the Ram.
Not sure on the new Ford.

 

[Piperflyer]

If I read my manual properly and if memory serves me correctly it has to be in tow-haul for the exhaust brake to function.

If I just put my exhaust brake on it will work. Doesn't have to be in tow mode.

 

[OEFVET]

On my GMC the exhaust brake works both in and out of tow mode. It can definitely be heard. However the most noticeable difference is the slowing down rather then coasting. The easiest way to see if it's working is to turn on the exhaust brake and put your truck in cruise control at 55mph. step on the accelerator and increase speed to 65mph. Let off the accelerator and you will immediately slow back down to 55mph. To see the difference shut off your exhaust brake and again set your cruise control at 55mph. Now accelerate to 65mph then shut off the cruise control and let off the accelerator. You will coast as opposed to braking. It will be very noticeable.

 

[Garypowell]

So far so good.....but don't miss my comment that it seems the only thing that seems to slow me down is the transmission downshifting. Part of my question....but not mentioned.... is this sometimes takes the RPM's up close to 4,000....which I really don't like. You want to talk about noise.....that gets noisy.....and as said....don't like it.

I have tried it with the cruise control and it does maintain my speed going down hill....again with a significant amount of down shifting. But frankly I don't mind gaining a little speed going down.....mainly want help stopping with the exhaust brake.

So specifically to Piperflyer and others with my truck......does your exhaust brake work by itself or do you get a lot of downshifting?

 

[OEFVET]

The exhaust brake needs back pressure to work effectively. The down shifting creates the needed back pressure. 4,000 RPM's on steep downhill is normal and tells me your exhaust brake is working. If you don't like the high RPM's I would recommend changing your transmission to manual shifting. Using the + - on the shift lever.

 

[mlpeloquin]

The GMC exhaust break works when you select it. No rig or rig in tow mode or not. When going down hill apply the break, release, apply it again, and release. The transmission may or may not down shift, but you will definitely will here and feel the exhaust break. I even feel it just slowing down for a traffic light with out towing or in tow mode. Tried it a few times. So if you do not feel or here it, go get it checked out.

 

[Miltp920]

Love this thread. NEW to the exhaust brake as my 03 did not have one, but the 16 does. 4000 rpm, wow, glad I read that here before I see it on the rpm gauge, as I would not have expected 4000 rpm. Going to try out the "tests" described. Thanks always, love this forum.

 

[TravelTiger]

Tony says you do have to tap or push the pedal to get it to engage, works really well on the 6% grade hill (aka Ranger Hill) on I-20 near us. We haven't had our 2013 GMC towing in the "real" mountains yet.

 

[alexb2000]

I just went over Wolf Creek pass (6.8% @11K' with lots of sharp turns) in Southern CO (South Fork to Durango) Followed by a friend in his 2015 Chevy 3500. We talked about it before going and he was under the impression that 3 or 4 thousand RPM would destroy the motor so he was always trying to get it to shift. Anyway, good thing we talked about it since Wolf Creek is one place you need to have an exhaust brake and some RPM for it to work. With any of these trucks you can now go down these passes pulling a 5er without ever (or rarely) touching the brakes. Really incredible capability in a light duty truck.

 

[porthole]

Simply put the question is how do I know my exhaust brake is working?

I push the button on the dash, it lights up. The DIC says that "Diesel Brake is Engaged". But I can tell no difference between having it on and just using Tow Mode when stopping/slowing down. My transmission downshifts like crazy in either mode (and various combinations). I thought I was getting an exhaust brake not a transmission downshifting brake.

I assumed that I would not hear the BLAM, BLAM, BLAM....like the big rigs....but I hear nothing and as stated above feel nothing......so what am I missing here?

In Florida I could not tell any difference and thought.....well....I'm in Florida. Now out in Wyoming and Utah I am seeing some 6 - 8 - 10% grades. On the way down the grades have played with various combinations.....and see no difference in braking between tow mode and when the exhaust brake is turned on.

You don't have an exhaust brake, you have a turbo brake.

With the Allison in the GM, when you engage tow/haul mode there are several things happening, Mainly the transmission up and down shift points are raised to put the truck more into the higher torque band and to add the higher RPM's for more effective engine braking (regardless of the type of retarder). The other main addition is the increase in transmission line pressures to aid in keeping the clutches engaged under the heavier loads.

The engines computer controlled power management should not let you do something to damage the engine, such as over revving. And to see close to red line operation on downhill traverses is not unusual, although the noise can be a bit unnerving.

When the engine braking is active, downhill, under load, foot off the pedal the turbo charger has vanes that can be manipulated by the PCM. Closing these vanes effectively limits the amount of exhaust that can go through the turbo, and this is what is slowing down the vehicle.

You should feel a difference, you may or may not hear any difference and you defiantly will not get the noise some over the road trucks make as the retarding used on those vehicles is technically not even an exhaust brake (Jacobs brake Jake brake)

This post has a couple of videos that show what a VGT (variable geometry turbo) or VNT (variable nozzle turbo) is actually doing to aid in braking.

Don't remember on the GM, but tapping the brake pedal on the Ford just starts the aggressive downshifting, turned on the braking is engaged. The RPMs just help.

The cruise method Chris mentions above should be a good way to try it out.

Ford, GM and Ram all use the same method now, a concept started by Banks Engineering on the 2006 GM Duramax.

 

[Bob&Patty]

The GM "exhaust brake" is trans downshifting and turbo vanes moving. I love mine....tap the brake pedal and let'er run down hill. Most of the time I never have touch the brakes again. Roll down your window and you will hear a slight popping/gurgling sound. BTW, with the new truck I have never used the tow/haul mode as I feel it's not needed for pulling or slowing down.

 

[dlw930]

We've been in and around the mountains for 6 weeks. Before we came, I studied the manual for our 2011 Silverado 3500HD dually. It said if you activated "Tow/Haul" mode, exhaust/engine brake, and set the cruise control for the desired speed, the system would maintain the desired speed automatically. So far, that has worked like a charm on steep grades. The trick is knowing what speed to set on the cruise control. That's a function of the grade steepness, the curves, etc. I've used everything from 35-60 mph for going down grades.


Sent from my iPhone using Tapatalk

 

[mikeandconnie]

My 2011 3500 works wonderful using the cruise control. I have taken most the grades in the lower 48 and it held the speed just fine.

 

[Garypowell]

Thanks all! I think I get it.....I really don't have an exhaust brake I have a variable vane turbo charger exhaust restrictor. I guess they call it an exhaust brake because the full title would not fit on the switch.

OK, I am being sarcastic since "exhaust" is involved and it does end up braking my truck.

Very thankful for all that contributed but Porthole helped me understand better Thanks!

Leaving UT (Fillmore) Saturday and going to Moab for a few days before we go across Colorado. I'll have plenty of time to play with all of this in view of my new knowledge. I had tried the cruise control method but was somewhat discouraged by the high RPM. I understand that better now...and might get used to it.

And I have learned that the cruise control method can be restricting when you pass someone and then let off the "gas".....the system kicks in and slows you down quickly by downshifting. When I am using that mode with the exhaust brake I have learned to turn off the cruise and then coast down to the set speed and then reengage.

 

[OEFVET]

I have found this to be very effective. Especially since your hand doesn't have to leave the steering wheel. Just deactivate and reactivate the button on the wheel.