Terrible highway pulling power

[Trent Gonzalez]

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. 

[Grumpy Bear]

A Semi is rated for 88K and struggles up inclines. You expect too much. 

It won't do 80 up a 5% grade?

[MrGraff]

If your leaving it on auto shift mode and cruise control on inclines then that's your first problem.  When Im approaching a good incline, I go into manual mode and let the engine get up in rpms or boost and it usually holds speed or increases speed.  That being said, my experience so far towing with the 10spd has been night and day difference vs the old 6 spd.

[XY74]

I would look closely at your aftermarket parts and verify nothing is wrong there.  Sounds like it's starving for air.  My trailer is about 9000 lbs and the truck has no trouble with grades at all using the cruise control.  Mine is all stock.  

[Keith_Schumaker]

^{I have a drw, but it has the same running gear so it should have the same power.  My camper is 17k and I am able to keep it at 65 on 5-6% grades,  I haven't tried 80 but I wouldn't doubt that it would be able to as it doesn't struggle at all at 65 even if I have to accelerate a bit to get around a truck on a hill.}

[Trent Gonzalez]

Going to try a couple things:

1. New map sensor

2. New fuel filter. 
 

low end power is awesome. Going to rule these two impactful things then go from there. Does truly feel like it’s starving for air and/or fuel. 

[2021 HD]

You are close to 18,000 lbs truck and trailer. You expect it to do close to 100 MPH up hill? If I was pulling that much I would go no were close to that speed. What happens when a moron cuts you off than slams on the breaks? I will tell you dead moron and your truck totaled.

[Jrscrib]

With the aftermarket parts this is not a surprise as most of them take power and fuel mileage away. I have no problems pulling 16k in mountain terrain 5-7 % with cruise control at 74 mph. Truck is stock and pulls better than my 18 did with same fifth wheel. We have a 9% grade hill that we pull from stop at the bottom and let off for a corner about three quarters of a mile up at 55mph. The ten speed makes a big difference in the pulling on hills. I will say aftermarket intake parts I have seen take power and fuel mileage away on any engine specially on diesels.