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The L5P did something strange to be aware of , while towing......

I was pulling the 5th wheel ( 15K ) on the Interstate. previously I had some wiring issues with the 7 pin from a poor install so I had the E brake on along with tow haul....( in case I lost trailer brakes again ) .... I fell off a 7% grade and the rig sped up to 74 from 70 as expected. I had planned to feather the brakes and let it roll out. Much to my surprise the truck downshifted to 4th and the tac hit 5k. I assume this was the E brake trying to help out.

Other than needing new britches there was no harm and no foul BUT the road was dry. What if she pulled this BS on a wet road? I would have folded up like a house of cards .

I don't believe Ill be using this combo anymore. I didnt think the E brake was active unless I hit the brakes. That doesnt appear to be the case.

Be safe

PS: 15K trailer, 2400lb pin 21600lb gross rig. 9 mpg avg and less power than the LML but same mpg. What a deal.
 

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:rof It is doing what it's designed to do. D mode on the shift selector. You should try the gear limit L mode. Lower gear beginning downhill helps hold speed.
 

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The L5P did something strange to be aware of , while towing......

I was pulling the 5th wheel ( 15K ) on the Interstate. previously I had some wiring issues with the 7 pin from a poor install so I had the E brake on along with tow haul....( in case I lost trailer brakes again ) .... I fell off a 7% grade and the rig sped up to 74 from 70 as expected. I had planned to feather the brakes and let it roll out. Much to my surprise the truck downshifted to 4th and the tac hit 5k. I assume this was the E brake trying to help out.

Other than needing new britches there was no harm and no foul BUT the road was dry. What if she pulled this BS on a wet road? I would have folded up like a house of cards .

I don't believe Ill be using this combo anymore. I didnt think the E brake was active unless I hit the brakes. That doesnt appear to be the case.

Be safe

PS: 15K trailer, 2400lb pin 21600lb gross rig. 9 mpg avg and less power than the LML but same mpg. What a deal.
Did you have cruise control enabled? If so, what's to complain about? That's exactly the desired behavior; if EB is switched on, cruise control will command the EB to actuate in order to limit speed on descents. It's a beautiful thing.

As for the slippery road surface, it would probably take more than just a wet road to break the traction on the drive axle. Ice and snow are a different story, but under those circumstances, you should not have EB enabled in the first place. That's the driver's responsibility, not the truck's.
 

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I tow a rig a little heavier than yours. My understanding and experience with the Exhaust Brake (what I'm assuming you mean by E brake) is that it won't take action til you push on the brake pedal so if you didn't push on the brakes before the downshift you must have been on cruise control. If you were on cruise control then that would definitely downshift as your speed went up on the downgrade. Sounds like you were going pretty fast to start a 7% downgrade. I get my speed down to around 45 before cresting a grade like that. If you're going fast and a downshift occurs engine rpm will go high quickly as you experienced. I had a similar experience driving through some hills and got surprised by an unexpectedly steep downgrade on one of them (i.e. I was going faster than I should have been). I stabbed the brakes to control my speed & the E brake downshifted the trans causing engine rpm to go to around 4500!! So lesson learned for me.
From what I've read the engine rpm limit during braking is 4800 rpm, for powered speed it's 3450 rpm. If this isn't right someone please chime in.
 

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Exhaust brake works when you off the throttle. The lower the gear the strong the braking effect. I go downhill in a gear that will hold the speed. These new trucks I don't really even need to use the brake pedal going downhill.
 

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so I had the E brake on along with tow haul....( in case I lost trailer brakes again )
Why would you NOT have everything engaged when towing?
Are you saying that you only let the full tow beast loose....IF you're trailer brakes aren't working? 'dunno;

From your descent description, I think you may be confusing the Grade braking with the Exhaust brake, which do work together but are different in how and when they rise to the occasion.

Add the cruise control in with the two, and everything changes again in how aggressive it gets.
 

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So I know GM markets these trucks as get in, turn on exhaust brake, tow haul, set the cruise and go.

BUTTTTTTTTTT....

sometimes you have to be smarter then the truck with your driving. Those issues could have been avoided by selecting the appropriate gear before hand on your decent. The situation you decribed is how GM set it to work. Try a few combinations of driving when towing.

I have found, on long climb or long downhill section to use tow haul, exhaust brake and manually shift the truck before it wants too.

I have also found if you are doing exactly what you described but werent in cruise, the down shifts aren't as aggressive. I think the issue is the cruise waits the 5 km/h difference before reacting, which in some cases to long.
 

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My 5vr is almost the same weight as yours.

I have towed my camper through the mountains of WV, TN and NC. While not as big as the ones out west, it can still be something to watch as you descend down the mountains.

For me, I am always in T/H mode (don't have exhaust brake and never use cruise while towing) and have never had an issue.

As others have already pointed out, you must be cognizant of your speed PRIOR to the downhill grade to keep you out of trouble once you begin the descent.

What works for me is to let the Max/Ally combo do what it was designed to do. The first time that I saw 3500 RPM on the descent, it really bothered me. However, after speaking to various GM dealers and Allison, that is what it is designed to do. My truck will maintain ~ 45 to 50 MPH on a 7% grade and I never have to touch the brakes. Have towed about 10k miles in and out of the mountains without issue.

I think that the best advice that I can give is that when towing, never let the rig get in front of you and always be prepared for the unexpected as it is incredibly hard to stop a 25k rig on a 7% grade if you are not prepared to do so.
 
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I had the same issue in my truck. Now when coming down a steep grade I will put the truck in manual mode (along with having tow/haul and engine brake on) and use the manual shift buttons to select the correct gear.
 

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Hello, new to the group.
I have a Chevy 2016 2500 4X4 four door 6’6”” box (I guess standard box for trucks today) 373 gears .
I’m looking at a Fuzion 5 th wheel 40ft toy hauler dual axle,Hitch 3055lb, 14050lb dry 1700lb full. Doubt I’ll ever pull full if so not far.
Am I at a comfortable range? I plan on airbags in near future ,just on safe side
Thanks in advance,
Railman
 

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Hello, new to the group.
I have a Chevy 2016 2500 4X4 four door 6’6”” box (I guess standard box for trucks today) 373 gears .
I’m looking at a Fuzion 5 th wheel 40ft toy hauler dual axle,Hitch 3055lb, 14050lb dry 1700lb full. Doubt I’ll ever pull full if so not far.
Am I at a comfortable range? I plan on airbags in near future ,just on safe side
Thanks in advance,
Railman
You need a Dually for that rig
 

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Hello, new to the group.
I have a Chevy 2016 2500 4X4 four door 6’6”” box (I guess standard box for trucks today) 373 gears .
I’m looking at a Fuzion 5 th wheel 40ft toy hauler dual axle,Hitch 3055lb, 14050lb dry 1700lb full. Doubt I’ll ever pull full if so not far.
Am I at a comfortable range? I plan on airbags in near future ,just on safe side
Thanks in advance,
Railman
Pin weight is killing you here. Definitely in dually land with this rig.
 

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I pull 40ft and longer 5ers all the time that typically always weigh over 14k, sometimes closer to 16k. It's no problem with a dually and air bags are nice too. I used to pull like that with a 6.0 gasser single wheel 3500. Air bags were virtually a must on it. I see guys pulling the big 5ers with single wheel trucks all the time. It's doable if you're not going far but the dually is much less squirmy. I'd never go back to a single wheel truck for such rigs unless i expected only sporadic short hauls.

Not knowing if that Fuzion is new or not, one other thing to keep in mind is brakes. The integrated brake controller on my 2012 will not actuate disc brakes on the newer rv's without modification. I'm assuming your 2016 is the same. Of course if it has electric drum brakes, no problem.
 

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I pull 40ft and longer 5ers all the time that typically always weigh over 14k, sometimes closer to 16k. It's no problem with a dually and air bags are nice too. I used to pull like that with a 6.0 gasser single wheel 3500. Air bags were virtually a must on it. I see guys pulling the big 5ers with single wheel trucks all the time. It's doable if you're not going far but the dually is much less squirmy. I'd never go back to a single wheel truck for such rigs unless i expected only sporadic short hauls.

Not knowing if that Fuzion is new or not, one other thing to keep in mind is brakes. The integrated brake controller on my 2012 will not actuate disc brakes on the newer rv's without modification. I'm assuming your 2016 is the same. Of course if it has electric drum brakes, no problem.
Thanks for reply . I was looking at new Fuzion. I thought I would be pushing it but , you know RV dealers will say anything to make a sale.
They assured me I’d be good but did suggest air bags .
 

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You can throw airbags on anything to make it level, all the carnage happens when you get out on the highway. RV salesman, have to go for a shower after talking to one of them:laugh:
 
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