Chevy 3500 HD exhaust brake question

[porthole]

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.

You are doing yourself a dis-service Bob. The Tow haul mode increases line pressures in the trans, which is beneficial for the transmission when you are towing something that combined is 3 times or more then the original weight of your vehicle.

 

[JWalker]

You are doing yourself a dis-service Bob. The Tow haul mode increases line pressures in the trans, which is beneficial for the transmission when you are towing something that combined is 3 times or more then the original weight of your vehicle.

Duane, I generally do not use tow haul mode when towing with this truck. Are you saying it's beneficial using the tow haul mode when going down the mountain or is it beneficial all the time? Thanks

 

[porthole]

Don't know with the RAM Jamie. With the Allison, the line pressures are boosted in TH, so all the time when towing, especially on hills, up or down.

You have mechanical sense, look into the operations of the 2016 RAM and whichever trans you have. I'm sure RAM, like GM and Ford, don't add the feature just because it is a nice to have feature.

 

[Doublegranch]

Jamie:

I would recommend you give the Ram Tow Haul a try! you will be amazed in the difference and won't hardly touch your brakes if you use it in conjunction with your EB. While Tow Haul will work without towing, I only use it when pulling.

 

[JWalker]

Jamie:

I would recommend you give the Ram Tow Haul a try! you will be amazed in the difference and won't hardly touch your brakes if you use it in conjunction with your EB. While Tow Haul will work without towing, I only use it when pulling.

Do you use the tow haul mode with the EB on the full or on automatic?

 

[travelin2]

I agree with the previous several points. We traveled from home north on US 15 a nearly 1500' elevation change with at least 5 uphill/downhills last evening. North of Williamsport, cruise set at 63, T/H on, speeds maintained uphill and down, almost like having autopilot . Never knew the BH was in tow.
Like mine a bunch!!!!


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[Doublegranch]

Jamie:

Coming back from Elkhart I used the EB on Full all the time....I later discovered that by using Auto I could free wheel when it wasn't required to slow down on the Interstate....but for 99% I will use Full when hooked up...I am not use to the auto setting as my previous Ram's were all manual and only the on or off settings.

 

[Bob&Patty]

Duane, you have point, but with the power this truck has I don't feel that T/H mode is needed. Now if I was pulling a 365 LM that would be a different story. When pulling our 14K Horn, I set the cruise at 62 MPH and let it run up hill and down hill. It never struggles and stays at 1650 RPM's pulling up hill. Very seldom does it even come out of lock up.

 

[porthole]

Bob, the power is good, the T/H increases the trans line pressures so that the trans can handle the additional loads and power being applied pulling the load with less stress.
How well it feels is not the reasoning behind using the tow haul mode when you are - well - towing or hauling.

Do as you please with your truck.

But, if I have 600+ ft lbs plus of torque twisting through my transmission, I would rather have 120 psi of plate pressure over 80 psi of plate pressure (guessing at the clutch plate pressures there)

 

[Bob&Patty]

Duane, don't know what happened to some of my last post. 1 whole paragraph disappeared. The WIFI in this CG sucks sometimes. Going to the National in Vegas, I will try your advise. BTW, the torque is closer to 800' ft lb's in '13 GM trucks. I had a scan tool connected when pulling a 7% grade at 62 MPH and the engine was 764' ft lb's. Just saying.

 

[porthole]

Do some research on the Allison. It is an excellent transmission, with only one minor drawback (outputting trans cooler pressure while cold, which is what causes those three trans lines to develop leaks)

The 600+ number was generic, giving some of the older trucks some breathing room.
The trucks will output up to the programmed limit, 800 or so for yours and 940 for the 2017 Ford.
But whatever the max HP and torque are, they will output what is needed under the current load.

 

[Bob&Patty]

Yep, had some coolers lines leak on my "07. I have not heard of any newer ones with that issue. I do stop by the Chevy store I worked at for many years. The trans guys that I worked with all tell me on the newer trucks, T/H helps but not as much as it did the older Allison's. Apparently they are new and improved over the last few years. But, like I said I will try your advise and see if I see any difference.

 

[Garypowell]

Just a quick update. Since the help from those above....I now understand how the brake works. Knowing that it varies the vanes and uses downshifting I can drive with more confidence.

In particular I drove from Fillmore, UT over to Moab, UT on Saturday. Had a few 6% grades which allowed me to play with the setup while going down a grade serious enough to make me "need" the braking system but not too hairy that I was overly concerned for our safety.

What I found out was that you have to work with the cruise control speeds to get the best braking with less revving of the engine. For example on those 6% grades if I told the Cruise control to hold at 60 MPH the engine revved up to 3,500 - 3,700 RPM. But if I told the cruise system to hold at 65 MPH the engine only revved to 2,500 RPM which is obviously a more comfortable number for me.

I understand that every Rig and truck combination with its weight, etc is going to be different....and so are 8% and higher grades for me....but at least with my new understanding I am getting more comfortable with how this all works.....so a big thanks to all who helped!

Of course tomorrow school is in session again as we head across 70 into Colorado. By the time we hit Kansas I'll be an expert but will probably forget all this by the time we come back this way. Or maybe I'll get brave and do I-40 between Knoxville and Asheville every so often to keep in practice. I've not been up or down Black Mountain for many years....can't say that I have missed it though! I lost a transmission once going west to east....and had a fuel leak develop going east to west in the 90's.....so I have generally gone around it ever since.

 

[danemayer]

Try slowing to 35 mph. On some steep descents, like I-70 from the Eisenhower tunnel to Silverthorne, there are signs that vehicles with GCVWR > 26,000 lbs have a speed limit of 35. Many of us are right around, or over the 26,000 lb limit and we should slow down on descents.

 

[Garypowell]

Thanks Dan.....I do believe tomorrow and Wednesday will be a little hairier. We are only going half way the first day to Glenwood Springs and then on Wednesday to Arvada where we spend the night in my nephew's churches parking lot.....first time to dry camp!

 

[travelin2]

Try slowing to 35 mph. On some steep descents, like I-70 from the Eisenhower tunnel to Silverthorne, there are signs that vehicles with GCVWR > 26,000 lbs have a speed limit of 35. Many of us are right around, or over the 26,000 lb limit and we should slow down on descents.

Thanks Dan.....I do believe tomorrow and Wednesday will be a little hairier. We are only going half way the first day to Glenwood Springs and then on Wednesday to Arvada where we spend the night in my nephew's churches parking lot.....first time to dry camp!

Do as Dan suggests...when I see a sign that truck speeds are xx mph, I set the cruise about 5 mph less than I want to travel downhill. This compensates for the over-speed of the cruise setting. I let the engine rev. Took a bit to get used to but the computer hasn't let it over rev yet. The computer controls the shifting and matches the speed accordingly. Doesn't mean I haven't braked a bit to slow down but I quickly hit "resume".


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[Nbomar]

Something else the T/H does on the newer Allison trans is locking the converter in 2nd-6th gears. Without the T/H engaged it only locks up in 5th-6th. Just an FYI.

 

[porthole]

Something else the T/H does on the newer Allison trans is locking the converter in 2nd-6th gears. Without the T/H engaged it only locks up in 5th-6th. Just an FYI.

The trans programing has been that way since at least 2006. Helps at least two ways, one is allowing more of the engine torque to be delivered to the drivetrain without TC slippage, and as a result of less TC slippage, the trans fluid temperature is kept lower.

 

[LowOnCash]

Hey guys the one most important point is unlike a standard exhaust brake that activates as soon as you let off the throttle, the GMC brake only works when you apply the brakes. No brakes no Exhaust brakes. Another way you tell it engaged other than sound and feel, is it has a soft release which means it can take a few minutes before the transmission will up shift again to a normal gear again.

In other words its a smart brake that totally stupid, instead of the driver applying the brake as he wants some pencil-head at GM had a better idea and made it different than millions of other exhaust brakes.

Ride Safe - Mike

 

[Dahillbilly]

Hey guys the one most important point is unlike a standard exhaust brake that activates as soon as you let off the throttle, the GMC brake only works when you apply the brakes. No brakes no Exhaust brakes. Another way you tell it engaged other than sound and feel, is it has a soft release which means it can take a few minutes before the transmission will up shift again to a normal gear again.

In other words its a smart brake that totally stupid, instead of the driver applying the brake as he wants some pencil-head at GM had a better idea and made it different than millions of other exhaust brakes.

Ride Safe - Mike

2023 3500HD works without using the brake when under 40mph, really well when in tow mode