2021 GMC Sierra 2500 consumer reviews

Bought the vehicle with 97,000 miles on it. within 10,000 miles had to replace injector number three. First winter all three heating element’s went out. Took it down to have it serviced and the tech found a leak coming from the transmission upon further inspection. The seal before the torque converter was already bad and leaking after that was replaced. We hooked up to a toy hauler and went on a trip halfway through the trip the truck Started a slight shaking. When we got back, went to the dealership and they said I had bent a rear axle. This was a bumper hitch toy hauler. And came in at under 10,000 pounds so tell me how a 2500 heavy duty truck is supposed to pull anything if the axles under that small of weight. Back up camera has gone out intermittently a few times as well. I highly recommend looking at a different truck if you’re looking for a three-quarter ton. Also don’t be fooled by the Allison sticker. It’s not a true Allison transmission and probably will never hold up to the standard that Allison is known for. I I definitely will be trading it in.

This thing has been a nightmare since we bought it. We purchased it used in 24 with 100k miles. A few months later it blew a head gasket and had to have a new engine put in. Since then it's been chasing down intermittent, random check engine codes and losing coolant to which we can't find the source of. The multipro tailgate is a pain and only works half the time. Sometimes the radio freezes. "Service steering column lock" message intermittently. Clunking shifting and hesitation around 55mph. It goes on and on. Between our own pocket book and the extended warranty, over $30,000 has been spent in repairs. Yes, you read that right, 30k. Biggest piece of garbage ever.

I love my 2021 GMC Denali 2500HD. I have gotten more complements on this truck than any other vehicle that I have owned. I get great highway fuel milage average 19-26mpg,which is great for a heavy duty truck!

Love my GMC. Owned a Chevy and this absolutely beats it hands down. Never had any issues. Inside is very comfortable and can't imagine driving anything else

First GMC, last GMC. Buyers, run in the other direction from the 2021 GMC Sierra 2500HD Denali, or live with daily, expensive regret! This is the worst and most unreliable vehicle I have ever purchased (new), and I have had many new and used. Steer clear of this year, make, and model! Expect mechanical failures, issues and annoyances you will never get resolved despite numerous trips for diagnostics and repairs, even if the issues are known and popularized. And expect to have your vehicle in the shop for weeks-months annually for unsuccessful diagnoses. And good luck with getting quality dealership service, even if taken out of state to give other locations a chance. This truck has persistent ac and defrost issues over 1500 rpm from day 1 with no resolution, makes desert summers and any winter driving miserable. Your only saving graces are keeping towels on hand to “defrost”, and cooled front seats for hot days - when they work! So expect to drive under the speed limit or without pushing the truck too much on inclines if you want to have ac/defrost conveniences. Multiple sensor failures/errors - too many to mention. Recurring blown fuses and issues with trailering system - as in several times per month - dealerships “see the messages but can’t find a problem. Recommendations made - keep boxes of fuses on hand at all times. Repeat issues with braking system, even after service bulletin repair - brakes are slow to respond and most embarrassing squeaking ever heard. Also receive constant messages that “new brake pads are found”, with info screen saying there is 0 front brake pad life. One of my other least faves is that the camera system that is played up with the extensive angles is useless for the views you need the most - Misaligned reverse camera - off center, negating use of the camera for hitching. “Split” in camera view that appeared after first service appt to resolve the recurring screen blackout makes using the camera for centering vehicle between parking lines impossible - as you never know if the top part of the screen is accurate or the bottom. Dealership response - “we compared to others, and most have these same issues”. What?! Advisors feel this acceptable, “within spec”?! Zoom in on the photos of this make/model for sale - you will see this in most of them. Shaky steering column during ENTIRETY of every drive and loud rubbing when reversing and turning wheel to back out of spot or do 3 point turn - acknowledged by techs yet they “can’t find the issue”. Ongoing shutter error codes and check engine light - even with a service bulletin, if the light turns off before your appt (which occurs consistently), you are out of luck for repair. Truck chirps when going over bumps which is also embarrassing in parking lots, and it squeaks when you exit the vehicle - yet more anomalies acknowledged by the technicians but root cause/s unable to be identified. And then there is the occasional loud gear grinding when moving to 1st gear, the more often struggle of the transmission into 2nd and 3rd, and the vehicle lurching when trying to maintain slow speed in these gears while towing. The DEF and even fuel level gauges - completely unreliable; have had multiple mishaps at night in the boonies due to this (must keep DEF on hand at all times!). I have 5 roadside assistance packages that I subscribe to; yet none of them will help get this vehicle to a shop when you are stranded more than 10-20 mi away from a GMC dealership. So expect to pay much and often for your per mile towing rate for truck breakdowns. I could literally go on and on about the MOST stressful purchase I have ever made. You will find 95%+ of your issues either “cannot be reproduced” during your service appointments, are “within spec”, “can’t be figured out”, or “due to something different than your last visit” - in other words, this is how the game is played to disqualify the vehicle as an official lemon for lemon law purposes.

I have had my 2021 Sierra 2500HD Diesel Denali for less than a year now. I bought it because we are fulltime RV'ers hauling a 35' 5th wheel. The power is fantastic and feels like we're hauling nothing, even in the NC mountains. The looks inside and out are great as well. I love this truck...WHEN IT WORKS. I have had to have this truck serviced quite a few times already. The issues I have experienced so far are the camera system keeps going out randomly. Dealership says a software update was needed to fix it and completed. However the issue continues to occur. The stereo will go out randomly as well. Last occurrence I could not change the station or adjust the volume. Same suggested fix; Software update.(In the shop now...again). The DEF fluid gauge is completely unreliable. On multiple occasions the truck will say 200 miles till empty and will decrease power. Problem is that I just pulled away from filling up the DEF. Dealership fix is to use a manufacturer DEF fluid only. Lastly, I used the 4WD high for the very first time last week just to pull out of the muddy yard and get on the driveway. When I attempted to shift back into 2WD I got the dreaded "service 4WD". In the shop now. I can't see a scenario where I would buy this vehicle again with all of the repetitive issues. If you're shopping and considering this vehicle, consider it with extreme caution. This thing is an 80k turd bird.

This is the first diesel I have owned. The power is amazing and I really like the room inside the cab. This truck is a beast... Love it!

I love my Denali. Beautiful truck inside out. When I drive down the road all heads turn. I couldn't have made a better choice. That's Cortez for you good service.

Truck was bought specifically to our travel trailer. We have to wait for 1000 break in before we can tow the trailer. So far the truck is very quiet, smooth running, & comfortable to drive. We were pleasantly surprised at how much interior storage space is available. Having the bed steps before rear tires and in the bumper sides is very nice. Bed rails are even with my shoulders so the steps get used a lot.

First diesel, excellent fuel mileage, much more comfortable and roomy compared to my previous 2016 GMC 2500 New mirror location does pose issue with seeing people or cars (blind spot) Overall extremely pleased