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Discussion Starter · #1 ·
We just traded in a 2013 3500 Silverado for a 2021 Denali 2500 to tow our 38 ft, 5th wheel toy hauler. The newer truck has more gears, driving mode selections, and features, so I would like to hear some opinions on driving in mountain grades.

With the 3500, I would slow to 50-55 at the top of 6-7% grades, manually drop into 3rd gear (6 spd trans) and let the exhaust brake limit the speed. However, there were a couple times on one particular downhill run that I only dropped down to 4th and the rig started climbing up over 60 mph, so I applied the brakes. When I did that, it felt like I blew a front tire - steering wheel shaking like crazy. Both times I pulled over at the bottom of the hill and checked the tires. Never any issue. I suspect the front anti-lock brakes were kicking in, causing the steering to shake while the back tires kept traction due to the weight of the fifth wheel.

The trailer weight, tongue weight, etc., are all within the Denali towing specs for 5th wheel.

1. What is the suggested way to approach that hill with the Denali (10-spd trans)?
2. This vehicle has "grade braking" (letting your foot off the brake after hitting desired speed). Is that better than manually down shifting as I am used to doing? Is that for mountain driving without a trailer, or something else?
3. This vehicle has 2WD, 4 H/L, and 4WD Auto selections. I'm assuming I should just leave that in 4WD Auto?
 

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Going up a hill just put it in tow haul and let her do what she does.
The grade braking on the 20+ isn’t that great in my opinion, typically you will need the down shift on your own.
Leave it in 2wd


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2023 Silverado 3500HD Drw
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You have no need to be on pavement In the auto setting, that’s a waste.

The new exhaust brake system, doesn’t it require you to touch the brake to activate?


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Discussion Starter · #6 ·
Hmm... I never thought about cruise associated with braking, but I found Service Bulletin 19-NA-091 ("Subject: 2020 Chevrolet Silverado and GMC Sierra 2500-3500HD New Model Features", dated June 2019) with the following in the Exhaust Brake section:
"The exhaust brake is also tied to the cruise control system, allowing a set speed to easily be maintained, even over hilly terrain."
 

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Hmm... I never thought about cruise associated with braking, but I found Service Bulletin 19-NA-091 ("Subject: 2020 Chevrolet Silverado and GMC Sierra 2500-3500HD New Model Features", dated June 2019) with the following in the Exhaust Brake section:
"The exhaust brake is also tied to the cruise control system, allowing a set speed to easily be maintained, even over hilly terrain."
Try it and your skepticism will go the way of a Russian T-72 on the business end of a Ukrainian Javelin.
 

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As stated, set the Cruise with tow/haul turned on and let the truck do its thing. No need to downshift, or do anything. These trucks are engineered for this stuff. And if you are well within the weight limits of a 2500 you are not towing much weight, so you have nothing to worry about.
 

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Team,
I also just came through Utah mountains as we did a week trip in Moab. I was towing 12K lb 5ver that was towing a utility trailer with a Polaris toy. Prob net weight around 15Klb - maybe 15.5K Lb. I noticed a few things… compared to my ‘06 LBZ (now have a ‘21 2500)

Truck did AWESOME but a few questions that relate 100% to this thread:

1) why does the truck downshift SSSOOO hard going downhill. It will drop to 5th gear (or even 4th gear) with exhaust break on EVEN if you‘re staying at the speed set on speed control. Example: I was set in cruise at 65mph and cruise was holding strong in 6th gear, not even varying 1mph without touching the brakes, and it would down shift to 5th or even 4th and RPM went through the roof to like 4200rpm and I would get nervous so I would take over in manual and throw it in 6th and never touch brakes. I just don’t understand why the truck does that? Anyone else see this? I was in tow/haul and did engage exhaust brake.
-side note: one of the only things I HATE about the ‘21 is that when you go into “L” mode (Manual shifting) it drops you gears from where you are currently no matter what; uphill, downhill, flat. If you’re in say 9th on a flat, and approaching an uphill and hit “L” it will drop you say to 7th and you take over. I wish it would just move to manual in the gear you’re currently in and let you be the boss.

2) OK - so my truck is 100% stock with the exception of Edge Pulsar tuner. I like having the displayed data on the CTS2 but was not using a tune because I didn’t want to jack up my truck.
Anyway my question is does the stock truck setting refuel/backdown power if you’re EGT are too high. So I was pulling up a hill absolutely cranking. EGT hit 1400-ish and I felt like the truck “stopped fueling” - if that makes sense. Truck EGT’s stayed at 1430 (almost EXACT) and wouldn’t move. Even if I shifted from 8th to 7th or 7th to 6th, EGT were rock solid. This makes me think that the stock program is “limiting” the truck. I also felt like she had more to give even though my foot was buried to the deck? Anyone relate? A few of the 6-7% grades took me down to 65-70mph. West side of Vail pass is super steep (8%) and took me down to 57mph in 6th gear. Truck has more - I know it. My LBZ would go up Vail at 65mph.

3) Finally (sorry for long post) - I had a situation where my truck hit about 210deg motor temp (coolant temp) and fan kicked on. Right on - no issues. But that fan stayed on for about 30miles, even AFTER truck was back down to temp at 178-180deg (which it runs regularily - even unloaded). It was really annoying. Fan just wouldn’t shut down? Then all the sudden at 186deg it shut down on a flat. No rhyme or reason IMO? Also my gauge doesn’t read the same as my Edge? I don’t know why. Gauge will read about 210 deg… but Pulsar reads accurate it seems? Anyone got thoughts for me? (see photos)

Overall - truck is RAD. I love it. I am just trying to get used to the “Fancy-ness” and learning how to operate this pickup at it’s max/best WITHOUT jacking it up.

Appreciate orignal post author as it spawned this writing… I promise I can get my own thread if this doesn’t fit in.

Vehicle Automotive design Car Gadget Personal luxury car


Light Car Vehicle Speedometer Gauge




Thanks to all - Take care.
Austin
 

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Discussion Starter · #16 ·
Team,
I also just came through Utah mountains as we did a week trip in Moab. I was towing 12K lb 5ver that was towing a utility trailer with a Polaris toy. Prob net weight around 15Klb - maybe 15.5K Lb. I noticed a few things… compared to my ‘06 LBZ (now have a ‘21 2500)

Truck did AWESOME but a few questions that relate 100% to this thread:

1) why does the truck downshift SSSOOO hard going downhill. It will drop to 5th gear (or even 4th gear) with exhaust break on EVEN if you‘re staying at the speed set on speed control. Example: I was set in cruise at 65mph and cruise was holding strong in 6th gear, not even varying 1mph without touching the brakes, and it would down shift to 5th or even 4th and RPM went through the roof to like 4200rpm and I would get nervous so I would take over in manual and throw it in 6th and never touch brakes. I just don’t understand why the truck does that? Anyone else see this? I was in tow/haul and did engage exhaust brake.
-side note: one of the only things I HATE about the ‘21 is that when you go into “L” mode (Manual shifting) it drops you gears from where you are currently no matter what; uphill, downhill, flat. If you’re in say 9th on a flat, and approaching an uphill and hit “L” it will drop you say to 7th and you take over. I wish it would just move to manual in the gear you’re currently in and let you be the boss.

2) OK - so my truck is 100% stock with the exception of Edge Pulsar tuner. I like having the displayed data on the CTS2 but was not using a tune because I didn’t want to jack up my truck.
Anyway my question is does the stock truck setting refuel/backdown power if you’re EGT are too high. So I was pulling up a hill absolutely cranking. EGT hit 1400-ish and I felt like the truck “stopped fueling” - if that makes sense. Truck EGT’s stayed at 1430 (almost EXACT) and wouldn’t move. Even if I shifted from 8th to 7th or 7th to 6th, EGT were rock solid. This makes me think that the stock program is “limiting” the truck. I also felt like she had more to give even though my foot was buried to the deck? Anyone relate? A few of the 6-7% grades took me down to 65-70mph. West side of Vail pass is super steep (8%) and took me down to 57mph in 6th gear. Truck has more - I know it. My LBZ would go up Vail at 65mph.

3) Finally (sorry for long post) - I had a situation where my truck hit about 210deg motor temp (coolant temp) and fan kicked on. Right on - no issues. But that fan stayed on for about 30miles, even AFTER truck was back down to temp at 178-180deg (which it runs regularily - even unloaded). It was really annoying. Fan just wouldn’t shut down? Then all the sudden at 186deg it shut down on a flat. No rhyme or reason IMO? Also my gauge doesn’t read the same as my Edge? I don’t know why. Gauge will read about 210 deg… but Pulsar reads accurate it seems? Anyone got thoughts for me? (see photos)

Overall - truck is RAD. I love it. I am just trying to get used to the “Fancy-ness” and learning how to operate this pickup at it’s max/best WITHOUT jacking it up.

Appreciate orignal post author as it spawned this writing… I promise I can get my own thread if this doesn’t fit in.

View attachment 1099748

View attachment 1099749



Thanks to all - Take care.
Austin
This is from the same tech bulletin I mentioned above, the max braking RPM is way higher than powered RPM for the L5P, so maybe your 4200 RPM is the norm. Also, I think your post is fine on this thread. I'm wanting to hear what I should expect rather than freak out over something on a trip then research it afterwards.
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2006 LBZ, 2009 LML, 2022 L5P. 1993 6.5 parked in the shed.
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Noticed my dash coolant gauge and my Banks iDash are never the same on coolant (22 L5P). 210 dash is actually 185 ish, 160 is actually 110. Other gauges are spot on with iDash values. Surprised me, old 09 LMM van, the dash gauges are very accurate, same with my 06 LBZ.
 

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2018 Silverado 3500 LTZ Z71 L5P CCSB
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Noticed my dash coolant gauge and my Banks iDash are never the same on coolant (22 L5P). 210 dash is actually 185 ish, 160 is actually 110. Other gauges are spot on with iDash values. Surprised me, old 09 LMM van, the dash gauges are very accurate, same with my 06 LBZ.
Yes the ECT gauge on the trucks dash is a worthless dummy gauge. The Idash will show the correct ECT.
 

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They did that water temp gauge thing when the LML's came out, I believe. When the water temp is anywhere in about the 175-215 range, the dash gauge registers 210. My only theory is GM didn't want nervous drivers freaking out thinking something was wrong every time the gauge went up and back down a few degrees. My only question was, why did they pick 210 for "normal" when the engine was actually running at 185 almost all the time? Straight up on the gauge for normal makes sense but why didn't they label it 185 rather than 210? When I got my first truck like that I thought, damn this thing runs hot all the time.
 
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