general problems of the 2020 GMC Sierra 1500 - part 2

-transmission valve body failure, wheel lock up, abs event, loud bang and a flashing "d" on driver information center (dic) when lightly or moderately accelerating forcing an 8-7 or 8-6 downshift -when all four tires lock up at a high rate of speed, this puts the driver, the passengers, and all others on the road at risk for injury or death. -yes, the problem has been found in a document by my local dealer that this issue was added to my exact vehicle's service manual on 11/27/24. The document describes in detail the exact scenario I have been involved in multiple times. It is deemed as #21-na-275. It locks up the tires randomly to the vehicle in mid acceleration at any speed including 80 miles per hour in one instance for me. -yes, the dealership inspected it and found the issue to correlate with the newly added section to the service manual, 13333166. This document id is 5925530 and the added information to the dealership is #21-na-275. The GMC manufacturer has been contacted as of 3pm mst 3/14/25. Insurance doesn't deal with mechanical problems. The police will only be involved when there is death or injury. -no. The only warning that happens is simultaneously as the vehicle locks up the tires causing the driver (me) to inevitably try to save myself and others, swerving and trying to focus on not hurting myself or others but I did notice the "d" flash on one of these occasions. This is the most dangerous issue with a vehicle I have ever even considered. At any time, for any reason, all four tires can lock up at any rate of speed and cause multiple casualties. The way to fix this is to spend $3,000 which I am sure many people like myself do not have. This means there are thousands of these exact make and models of vehicles on the road right now. Please do not take this lightly as I have almost crashed multiple times with people in my vehicle due to no fault of my own.

Engine light would come on for a few days and than turn itself off. This occurred for about 8/9 months; however, instructed by the gm maintenance department that if the vehicle came in and the light turned off before they got to it I would be charged for the diagnosis and no work would be performed. Engine light came on and I was able to park the vehicle / they picked it up and read it prior to putting in their lot until a tech became available. Gm maintenance was able to diagnosis that there was an issue with the egr sensor and nox catalytic converter without filter failed / both items replaced.

The transmission is jerking and sometimes it will not shift enough to get out of others ways. Severe slippage in the transmission I have taken the truck to the shop 3 times for the same issue. Now they tell me I need a new transmission.

Vehicle was going in for warranty recall; however, I requested they look at the def system as my def gauge would bounce between full and empty; along with, alert me of going into limp mode. Gm maintenance updated the recall and noticed that the def tank sensor failed and required to be replaced.

See attached document for complaint.

I have taken my vehicle to 3 seperate mechanics (GMC, aamco and independent). They all agree that my valve body inside the transmission must be replaced. The problem is that valve bodies are on a national back order and cannot be fullfilled for months, putting my transmission at risk for further failure. Reading online forums, there are many GMC owners facing this same issue. The mechanics at GMC are requesting that I change out my entire transmission, since that will be a quicker solution than waiting months for that valve body. Now, I am being told that they are having difficulty locating an original manufactured transmission. This puts me in a serious bind because my truck is my only vehicle and there are no valve bodies or transmissions to fix this issue. My truck is only a 2020 and I just surpassed 100k miles. There were no dashboard warning lights that indicated my trucks problem. Only the fact that my truck is shuddering when shifting gears and that a diagnostic tool had to find the source of the problem. This problem started about 5 months ago and has progressivly gotten worse.

The contact owns a 2020 GMC Sierra 1500. The contact stated that while accelerating from a stop light, the rear wheels seized. There were no warning lights illuminated. The vehicle was diagnosed by a mobile mechanic with transmission failure. The vehicle was towed to the residence. The dealer was informed of the failure. The contact was informed by the dealer that the repair was not covered under warranty due to the mileage. The vehicle had not been taken to the dealer. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was 82,000. The VIN was not available.

Gm 10l80 speed transmission pump idler gear failure causing erratic shifting, lurching, or being stuck in gear. Dealer confirmed and recommended to replace the transmission. Transmission was replaced out of pocket in December. The issue is widespread on youtube.

Motor seized at 52,000 miles. . . . Replaced motor. . . At 72k miles, lifters and rods had to be replaced on the 2nd motor. Transmission also failure at 72k, being replaced.

The truck was dropped off on November 11th of last year due to a valve body failure, and I’ve been informed that repairs cannot be completed because the necessary parts are unavailable. I purchased the truck in late August of last year and am now stuck making payments on a vehicle I can’t even drive. When I approached the GMC dealer about trading it in or having them buy it back, they said trading it in was an option but couldn’t offer anywhere near what I paid. To make matters worse, they have no timeline for the repairs, and buying it back isn’t an option.

Def emissions warning and engine emissions warning lights suddenly appeared. Def emissions warning went on and off multiple times in the two days before bringing to a GMC service location. Informed that the def tank heater failed, a known problem, but that they likely would not have a repair available for over a month and would not be covered by any warranty. The vehicle is now speed limited to unsafe speeds on highways while waiting for the repair.

Hi I have always taken good care of my 2020 GMC Sierra 1500 at4 6. 2 kept up with its regular and recommended maintenance. I had no warning signs on the dash. So it surprised me that while on my way to work early one morning I was getting off the highway exit and the truck lost power, my steering wheel hardened and it posed a great threat to my life and others on the road, as it suddenly decelerated in a area where people are driving at accelerated speeds. The whole truck was loosing power and shaking hard as I attempted to steer it to a safe location on the side of the road. Had a mechanic inspect it and they determined the truck ended up with a seized engine. I have since not been able to use my truck for 8 months and still currently paying monthly payments of 1000 to pay it off.

At 103,000 my 2020 at4 5. 3l v8 had a p0307 code thrown. Cylinder 7 misfire. Driving highway speeds, sudden loud pop and then the service engine light came on and automatic braking engaged, and the idle got extremely rough. Ended up being a bad lifter, bent rod, tore lobe off of the camshaft. Roughly 8,000 for the repair, new cam, new lifters, spark plugs and coil packs. Now only about 3,000 miles later, driving, sped up to pass on the interstate and another misfire, p0306 this time cylinder 6. Same symptoms check engine light, automatic braking, rough idle. Seems to be another failed lifter and bent rod. Currently awaiting diagnostic for this second misfire issue. When speaking with the tow truck driver and the mechanic both mentioned a significant rise in cases like this. There is definitely something wrong with the design that the manufacturer needs to be help responsible for. I have less than a month ago replaced all the lifters only to have another one fail again.

There has been a recall on the 2020 Sierra 1500 for the driveshaft which causes shuddering and vibration which my vehicle is exibiting but my VIN is not on the recall list.

Transmission failed at 75,000 miles, yes it is available for inspection. Truck went into limp mode on the highway and turned into a very dangerous situation, I was barely able to exit the highway. Yes the dealership martys GMC in kingston MA has confirmed that it is transmission failure. My vehicle has been sitting on the lot of marty's GMC since September 13, 2024 waiting for a backordered part to fix the transmission at an estimated cost of $2,500. The warning check engine light followed by every single lamp on the dash appearing on [xxx] which is the date of transmission failure. After careful research of this issue I have found this is a widespread problem with this particular 10 speed GMC transmission in my 2020 GMC sierra that I am still paying car payments on. I have rented a vehicle at my own cost for the past 4 plus weeks to get back and forth to work. Information redacted pursuant to the freedom of information act (foia), 5 u. S. C. 552(b)(6).

The contact owns a 2020 GMC Sierra 1500. The contact received notification of NHTSA campaign number: 24v797000 (power train); however, the part to do the recall repair was unavailable. The contact stated that the manufacturer had exceeded a reasonable amount of time for the recall repair. The contact stated that there was a loud clanking sound underneath the vehicle while starting the vehicle. There were no warning lights illuminated. The vehicle had been taken to the dealer and was diagnosed with transmission failure. The contact stated that the transmission had been repaired twice however, the failure persisted. The vehicle was taken to the dealer again and the transmission was replaced. The dealer was contacted about the recall and confirmed that the VIN was included in the recall however, the part to do the recall repair was not yet available. The manufacturer was not made aware of the issue. The failure mileage was 50,000. Parts distribution disconnect.

The afm/dfm system in these trucks are making the engines and transmissions go out around 70k miles. The lifters fail right around the same time factory warranty runs out then your left with a 6 thousand dollar bill to have it fixed. I hope this becomes a recall because numerous people I talk to are getting rid of they're Gmcs and chevys and going elsewhere.

Engine light came on and real bad urine smell / burning coming from the vehicle / rough performance. This issue occurred at various speeds / trips / drive types with the only variation being speed from 25mph to 75mph. Vehicle went in to discover that the reductant control module software (rcm) out of date, and two nox sensor failures.

The transmission went at 67,000 miles and posed a safety issue when my husband was driving & suddenly couldn't drive above 1st gear. Vehicle is at the gm dealer and has been for weeks, but there have been so many issues with the transmissions of this year, make & model, that the transmissions are on back order and we are told it can be months before they get one in. The dealer already has another one that has been waiting for once since April. We know of others with this same issue on this make/model/yr, as well as engine issues, but yet there are no recalls for this issue. The only warning that came on was when the issue occurred- no prior warning or indications. Gm is involved but make no comment on why there isn't a recall for an obvious known issue.

Has happened three times. 1st and 2nd time driving down road towing trailer, rear wheels locked up for 12-15’ while driving 50-55mph. I had thought it was my trailer axel. Happened twice within 6 miles. 3rd time was 1 month later. Rear wheels locked up driving on interstate at 70-75 mph. I estimate that I traveled 1,800 miles between the 2nd and third incident. Vehicle is at the dealership getting inspected for repairs no warning lamps before, almost every warning light came on after incident if this happened on a wet, ice, snow or dirt road this could have caused a serious accident. It would also be bad in a curve. Dealer took for road test but did not have any luck recreating the issue. They checked the differential oil and it didn't have any heavy metals. They are going to take the differential apart to inspect it to verify. They checked my battery and said it needed to be replaced. Also a wheel speed sensor needed to be replaced.

Shuttering while in motion at a speed of 35mph or above. My 2020 GMC Sierra 1500 at4 carbonpro while driving at or above speeds of 35mph experiences a hesitation and severe shuttering while trying to maintain any speed of 35mph or above. The hesitation causes extreme vibrations and hesitation when lifting or applying foot to the accelerator. This happens in any drive mode also with cruise control on or off as well as shifting into low and being in any gear trying to prevent it. It also does this on any road and condition. It feels like a slip in the transmission or torque converter, possibly could be the rear end or variable valve timing as well. And when taking of from a red-light or stop sign it slips as if the truck has lost traction, but it hasn't. This is very dangerous and could be the cause of a serious accident when trying to accelerate. If your traveling at hwy speeds it feels as if the brakes are being applied and the tires are going over a washboard which could cause a collision, tire wear, or driveline damage.

Lifters failed in November 2023 and had repaired major engine damage including 4 cylinders, cam shaft, lifters, gaskets etc. After major repair work done. Truck is now doing same exact thing in January 2024. The dealership is stating they will not look at the vehicle unless I buy a new battery. I asked them to try a used battery to see if that makes a difference. And then if it is the battery I will replace. I was hung up on after the technician doug pedersen stated ill have a supervisor call you back.

This car had lifter motor failure at 135k miles and transmission failure at 145k miles, the torque converter of this truck is the culprit of many issues as the lifter issues.

Check engine and ecm errors. The dealer replaced one bank lifter. Shortly after, a similar issue was caused by reassembly. Approximate mileage: 30 k. A month later, the same issue, but this time the vehicle was not drivable, with very low engine power. The dealer stated lifter failure and camshaft damage, engine replaced January 2024, mileage 31 k. Currently 42k and had one instance of ecm error, which only lasted a few seconds, but the engine faltered and lost power. At the most recent oil change, the dealer said no error codes were present. Gm indicated that my VIN is not covered under the most current recall. Since the engine was replaced in 2024, there is virtually no possibility that the engine replacement was not a new engine and should fall under this most current recall.

-lifter failure on 6. 2 v8 engine, causing damage to camshaft -lost significant propulsion while driving on the highway, nearly avoided being rear-ended by another vehicle due to loss of vehicle propulsion -dealer had to to replace lifter bank and camshaft -no issues, once lifter failed dash lights all lit up.

The right side started clicking out of no where when I turn the steering wheel.

The contact owns a 2020 GMC Sierra 1500. The contact stated while accelerating from a complete stop, the vehicle lunged forward. The contact stated that the failure recurred while driving at various speeds depressing the accelerator pedal, and while decelerating to come to a complete stop. The check engine warning light was illuminated. Additionally, the contact stated that while coming to a complete stop at a traffic light, the vehicle lunged forward violently, as if the vehicle had been rear-ended. The vehicle was taken to quality plus automotive, where it was diagnosed that the transmission had failed and needed to be replaced. The local dealer, leith GMC (919) 366-1000), and other dealers were contacted and informed the contact that an estimate for the repair could not be provided because the transmission part was not available. The vehicle was repaired by quality plus automotive. The manufacturer was notified of the failure and referred the contact to the NHTSA hotline for assistance. The failure mileage was approximately 75,450.

Bearing in transmission failed at 75000 miles. Took to dealership and they said truck needs new transmission. Truck makes rattling noise in transmission pan. Dealer said that oil was full of metal shavings. Dealer also said that this was second truck in 2 weeks with same issue. No warning lights or check engine lights came on. Dealer advised that the transmission could fail and to park it until I can pay $6000 for transmission replacement. Dealer heard rattling and confirmed metal shavings. Transmission failure could result in traffic hazard or accident if transmission loses all drive ability.

Vehicle stuck in gear. Dealership was delivering the car back to myself when about a mile out from my house when the vehicles made a sudden downshift and was stuck back in gear. Driver called and notified me that it was on its way back to the shop for further work.

Vehicle drop in gear / down shift while driving on the highway. Went from 75mph down to 55mph due to high rpm revs.

My 2020 sierra slt always hesitates or stutters upon take off only on the very first start of the day every day. It appears to be a transmission gear issue or perhaps air/fuel issue. I also have had several different issues with my infotainment system. It screen changes from one screen to another on its own occasionally and it also has a very loud pop when I turn off my iphone xr from the trucks sound system as if it will crack my speakers. I have taken it in to two separate cavendar GMC dealerships in san antonio on 3 different occasions and they claim it does not do either. This cannot be the case as it does it for me every single day since I bought it from the showroom floor. They have said they have updated or reprogrammed both systems but I still have both issues. I am about to lose warranty coverage and I am afraid this will never be addressed. I am taking it in 1 last time. I will never buy another gm product!.

The truck has developed a shake that can be felt in the floor boards, seat, and steering wheel at highway speeds. It’s has spent several months at dealerships without being fixed. I have replaced tires, wheels, shocks, upper control arms, and the transfer case without success.

Consistent issues with my truck. It is a 2020 GMC Sierra 1500 VIN: 1gtu9det7lz288231. In April 2022, my truck started to exhibit concerning issues. I was worried about driving home from work and called the dealership I bought the truck at. They recommended that I take it to the the service center in frankfort, ky where I work. I drove the truck directly to neil huffman GMC. They declared the truck unsafe for me to drive. They set up rental car for me to use and I left the truck at the service center. They initially said it was the torque converter. Over the course of two months they kept finding more issues. Repairs were completed at neil huffman GMC service center located in frankfort, ky. My truck still has the following issues. . 1. Ringing sound 2. Grinding or clunking noises 3. Loud noise when I press the gas pedal 4. Delayed shifting and hard shifting problem I drive a hour back and forth to work everyday and don’t want the truck to have issues on the interstate. Driving with a bad torque converter is unsafe since it causes sudden stoppages and significant speed fluctuations. Worn or slipping transmissions have many warning signs. A damaged transmission creates a dangerous situation for me and for other drivers. I had an appointment at adams GMC in richmond, ky on September 1st. They said they couldn’t hear anything and no services were conducted. Neil huffman GMC service department said they replaced basically the entire transmission. I don’t understand why there would be issues still. Kyle moore.

The contact owns a 2020 GMC sierra. The contact stated that while driving at an undisclosed speed, the vehicle shuddered. The vehicle was taken to the dealer, but the dealer could not duplicate the failure. The vehicle was then taken to gilland Chevrolet GMC (3071 n us hwy 231, ozark, al 36360) where the contact was informed that the vehicle already had new transmission fluid filled in the transmission. The vehicle was not repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 42,000.

I purchased the 2020 Sierra 1500 because the label on the truck frame states that it can tow 9300lbs. Subsequently, in April 2021, I purchased a 34' travel trailer with a max capacity of 8995lbs. In August, I received a notice from GMC that they overstated the towing capacity by 500lbs. The new towing capacity is 8800lbs. GMC's response to my request for a refund was that they were not going to help me. Their solution is that I can be provided a new sticker by the dealer upon request. This does not resolve my issue, nor the issue of other sierra owners who purchased this vehicle because of its stated towing capacity. In doing research, it appears that in model year 2014, GMC faced a class action lawsuit for misrepresenting their capabilities. I believe that this malpractice is a safety concern for me and many others. Attached is the towing label on the frame and the letter from gm.