Chevy and GMC Duramax Diesel Forum banner
  • Hey Everyone! Enter your ride HERE to be a part of this months Ride of the Month Challenge!

1 - 20 of 49 Posts

·
Registered
Joined
·
17 Posts
Discussion Starter · #1 ·
2020 GMC Sierra 3500 SRW.

Since brand new, I’ve had terrible pulling power specifically on incline grades (as low as 4%-5%). I routinely haul 5th whee trailer, 10,000-11,000 lbs.

Prior to an incline I’m able to maintain 80mph no problem. However, as soon as I hit the incline, the truck bogs down to 65mph and I can’t increase my speed any more, even at full throttle. Truck temperatures are 100% within normal range and temperature has never been an issue.

Truck has a derringer, CAI, and Wehrli Fab intake horn.

No check engine lights so dealership isn’t able to find anything wrong.

These trucks are rated for 21,500lbs so it leaves me stumped why the truck isn’t performing. It has phenomenal low end power, but it just seems to struggle on the highway. Any help would be much appreciated.
 

·
Registered
Joined
·
1,182 Posts
starving for fuel???
 

·
Super Moderator
Joined
·
958 Posts
What level is your Derringer set to when you are doing this?
 

·
Premium Member
Joined
·
1,317 Posts
That isn’t normal. Mine is completely stock and pulls like a freight train at highway speeds going uphill. You might try removing the derringer and see how it runs.
 

·
Registered
Joined
·
17 Posts
Discussion Starter · #5 ·
What level is your Derringer set to when you are doing this?
I’ve tried all 6 levels of the derringer, and to be honest I purchased the derringer because I thought it would help it. Meaning I noticed the lack of performance first time I towed with it when the truck had about 500 ish miles on it.
 

·
Registered
Joined
·
17 Posts
Discussion Starter · #7 ·
That isn’t normal. Mine is completely stock and pulls like a freight train at highway speeds going uphill. You might try removing the derringer and see how it runs.
This is what I’ve heard which is incredibly frustrating. My old LML would have run circles around this truck. I purchased the derringer after I noticed the sluggish pulling power hoping it would help, so it was happening before the derringer was put on
 

·
Registered
Joined
·
1,079 Posts
How many miles are on the truck?
 

·
Premium Member
Joined
·
742 Posts
Maybe replace the fuel filter
 

·
Registered
2017, 2500HD, LTZ, front guard, Duraflap mudguards, Leer bed topper
Joined
·
786 Posts
What altitude are you travelling...?
 

·
Registered
Joined
·
1,764 Posts
2020 GMC Sierra 3500 SRW.

Since brand new, I’ve had terrible pulling power specifically on incline grades (as low as 4%-5%). I routinely haul 5th whee trailer, 10,000-11,000 lbs.

Prior to an incline I’m able to maintain 80mph no problem. However, as soon as I hit the incline, the truck bogs down to 65mph and I can’t increase my speed any more, even at full throttle. Truck temperatures are 100% within normal range and temperature has never been an issue.

Truck has a derringer, CAI, and Wehrli Fab intake horn.

No check engine lights so dealership isn’t able to find anything wrong.

These trucks are rated for 21,500lbs so it leaves me stumped why the truck isn’t performing. It has phenomenal low end power, but it just seems to struggle on the highway. Any help would be much appreciated.
Are you running stock tires? If not, are your tires' diameter?
 

·
Super Moderator
Joined
·
958 Posts
Did the truck have the problem before your mods? Something doesn't sound right or add up. Did you change wheels as well, or just throw bigger ones on the stock wheels?
 
  • Like
Reactions: cfell

·
Registered
Joined
·
17 Posts
Discussion Starter · #16 ·
Did the truck have the problem before your mods? Something doesn't sound right or add up. Did you change wheels as well, or just throw bigger ones on the stock wheels?
Long story short, I bought the truck brand new. At about 500 miles I hooked up the trailer for the first time. Noticed this insufficient power on the highway so I initially thought it was still going through it’s “break in period”. I’d never bought a brand new truck before so I thought that was the culprit.
Few months down the road I put 35’s on stock wheels and put a cognito leveling kit on. (Upper arms, torsion keys, fox shocks)
Towed the same trailer 2 more times and still experienced this unusual lack of power on the top end. (Bottom end has always been good)
So I figured I’d spend some money on a derringer and an intake. Thought maybe it needed more air and a small tune could help it. Felt like the truck wasn’t “opening up”. Put the derringer on around 7,000 miles on the truck and have towed the trailer 4/5 times since then and same thing.
The only alert I’ve ever gotten is “excessive torque converter clutch slip” on my derringer, but then it went away. Spoke with the techs at banks power and they said it’s a safety feature and if it happens again have a transmission tech look into it. Problem is, the service techs won’t look into it unless I get a check engine light on.
 

·
Premium Member
Joined
·
1,317 Posts
Look up Inglewood Transmission and call Mike. I don't know how much experience he has with the new transmissions but just see what he thinks about it. To me it's sounding like either a transmission issue or the turbo isn't giving all it can for some reason.
 

·
Registered
2017, 2500HD, LTZ, front guard, Duraflap mudguards, Leer bed topper
Joined
·
786 Posts
Restore to stock.

These computers, er, trucks/Duramax, are complex.. as you know. As you purchased new, I would suspect a 'relearn' for the whole system is in order. The transmissions learn.. the engine learns... me, not so much.

Dealer did install codes on our 2017 and it did change things. I figure they just let me drive to let it 'relearn' my own driving. But, then... on our Allison tranny there is a documented 'relearn'.. it tests many more than I thought it would...

I do not tow our 10k trailer over 65.. so, I will bow out now... Hope you get happy with the truck and will check in to see what your 'fix' was. Peace..
 

·
Registered
Joined
·
17 Posts
Discussion Starter · #19 ·
Look up Inglewood Transmission and call Mike. I don't know how much experience he has with the new transmissions but just see what he thinks about it. To me it's sounding like either a transmission issue or the turbo isn't giving all it can for some reason.
Thanks for the responses and resource, very much appreciated
 

·
Registered
Joined
·
17 Posts
Discussion Starter · #20 ·
Restore to stock.

These computers, er, trucks/Duramax, are complex.. as you know. As you purchased new, I would suspect a 'relearn' for the whole system is in order. The transmissions learn.. the engine learns... me, not so much.

Dealer did install codes on our 2017 and it did change things. I figure they just let me drive to let it 'relearn' my own driving. But, then... on our Allison tranny there is a documented 'relearn'.. it tests many more than I thought it would...

I do not tow our 10k trailer over 65.. so, I will bow out now... Hope you get happy with the truck and will check in to see what your 'fix' was. Peace..
Yeah, definitely worth a try. Going to replace fuel filter and take back to stock for a few weeks.
At this point I’m happy with it 99% of the time, truly do love it. Just had high expectations for its towing capabilities. I appreciate your suggestions, much appreciated
 
1 - 20 of 49 Posts
Top