Car was idling and parked. Warning code showed up on dashboard ESC, electronic stability control, reduced engine power. Vehicle then displayed transmission disruption, warning light displayed as well. I was able to drive it to the dealership but the performance of the vehicle was limited by the reduced engine power. Transmission was hesitating and clunky during gear changes. My sierra has 5,000…
2020 GMC Sierra powertrain problems
moderate 82 complaints filed with NHTSA · avg repair $2,500 · see powertrain across all vehicles →
Failure mileage
Complaints
82
Recalls
0
Avg fix
$2,500
When does it fail?
Of the 82 powertrain complaints filed for the 2020 GMC Sierra, here's the actual mileage breakdown — failures cluster heaviest at 0-25,000 mi.
0-25k
25-50k
50-75k
75-100k
100-125k
125-150k
150k+
Each bar shows the share of total complaints filed at that mileage range. Peak failure window highlighted. Some owners report problems earlier; some make it well past 150,000 miles symptom-free. Maintenance habits and driving conditions shift the curve as much as mileage alone.
What stands out
Owners have filed 82 powertrain complaints with NHTSA against this vehicle, but no formal recall covers the issue — the federal record reflects what manufacturers have admitted, not everything owners are reporting.
Powertrain accounts for 19% of all owner complaints filed against this vehicle, across 10 categories tracked.
The failure pattern owners describe
Owners describe sudden, unwarned transmission failures leaving vehicles stranded on highways and unable to shift into any gear—a recurring problem across dozens of complaints. Many failures occur between 40,000 and 100,000 miles, often accompanied by limp mode activation and reduced speed capability. Transmission parts sit on national back order for months, stranding owners with vehicles they are still paying for and forcing them to rent cars out of pocket.
Engine problems center on valve lifter and camshaft failures, particularly in 5.3L and 6.2L models, tied to the Dynamic Fuel Management system. Owners report loud knocking, power loss, and rough idle, with diagnostics confirming metal debris in oil and internal engine damage. Full engine replacement costs $8,000–$9,200+, often required after dealer lifter repairs fail again within weeks. One critical failure involves transmission valve body malfunction causing all four wheels to lock up at highway speeds—a safety hazard included in TSB 21-NA-275.
Transmission cooler lines fail at the crimped hose ends, spilling fluid and disabling the truck. Transmission shifting issues manifest as chronic shuddering and hesitation at speeds above 35 MPH, often starting at low mileage and worsening over months. Dealers frequently cannot reproduce the issues or find fault codes despite symptoms occurring daily. Other powertrain complaints include stuck-in-park failures, exhaust emissions system failures requiring seven repair attempts, and sudden loss of steering and brake assist while driving.
Same GMC Sierra powertrain reports on nearby years: 2017 · 2018 · 2019 · 2021 · 2022
Failure modes owners describe
Transmission Failure / Loss of Drive
Complete transmission failure with loss of all gears or sudden inability to drive, often without warning. Failures manifest as vehicle unable to move, stuck in limp mode, loss of power during acceleration, or sudden downshifts. Owners report catastrophic failures requiring full transmission replacement.
When: Mileage ranging from 11,000 to 146,000 miles; most failures between 40,000–100,000 miles
Symptoms owners cite: Complete loss of drive or inability to shift into any gear; Vehicle stuck in limp mode with limited speed; Sudden violent jerking or lunging, especially during acceleration or at traffic lights; Shuddering or shaking during gear shifts; Hard or delayed shifting; Loud banging or rattling from transmission; Vehicle unable to exceed 30 MPH after failure
Codes mentioned: Transmission software failure (unspecified), Transmission control module (TCM) failure, Valve body failure, Torque converter failure, Bearing failure in transmission
Repairs/costs cited: Full transmission replacement, $2,500–$6,000. Multiple owners report transmissions on national back order for months, unable to source replacement parts.
Recalls/TSBs owners mention: Recall 24V797000 referenced in multiple complaints; however, many VINs found not included in recall. Parts unavailable for recall repair. Warranty denied on out-of-warranty vehicles.
Engine Lifter / Camshaft Failure
Premature failure of valve lifters causing collapsed lifters, bent push rods, damaged camshafts, and metal debris in oil. Failures often lead to catastrophic engine damage requiring full engine replacement. Most common with 5.3L and 6.2L engines, tied to Dynamic Fuel Management (DFM/AFM) system.
When: Mileage from 30,000 to 103,000 miles; most failures around 70,000–85,000 miles
Symptoms owners cite: Loud rattling, knocking, or clanking noise from engine; Loss of power, bucking, or stalling; Rough idle or smoke from exhaust on startup; Rough acceleration; Engine shutdown with limp mode activation; Check engine light with misfire codes (P0307, P0306); Acoustic test confirms excessive wear or catastrophic internal damage
Codes mentioned: P0307 (Cylinder 7 Misfire), P0306 (Cylinder 6 Misfire), Check engine light
Repairs/costs cited: Full engine replacement, $8,000–$9,200+. Multiple owners report lifter replacement alone insufficient; dealers eventually recommend full engine swap. Rebuilt and new engines difficult to source.
Recalls/TSBs owners mention: GM declined assistance in some cases. Recall for 6.2L engine exists for similar issues; 5.3L owners report similar failures not covered under available recalls. Some owners report GM warranty covered repair; others denied.
Transmission Valve Body Failure with Wheel Lock-Up
Transmission valve body failure causing unintended rear-wheel lock-up at highway speeds, creating immediate loss of vehicle control and skidding. Multiple incidents at different speeds without warning. Related to TSB 21-NA-275.
When: Incidents reported at various speeds; $3,000 repair cost cited
Symptoms owners cite: All four tires lock up simultaneously at high speed (40–80 MPH); Violent skidding and loss of vehicle control; Loud bang before lock-up; Flashing 'D' on driver information center during acceleration; Forced downshift (8-7 or 8-6); No prior warning; occurs randomly during normal acceleration
Codes mentioned: 21-NA-275 (TSB document), Document 13333166
Repairs/costs cited: $3,000 repair cost cited. Multiple owners report same exact failure pattern.
Recalls/TSBs owners mention: Dealership found issue correlates with TSB 21-NA-275 added to service manual 11/27/24 for affected vehicles.
Transmission Cooler Line Failure
Transmission cooler line hoses failure causing transmission fluid leak and loss of drive. Failure caused by crimped housing at hose ends. OEM hoses were discontinued and replaced with newly designed version.
When: Reported on newer vehicles
Symptoms owners cite: Transmission fluid leak; Vehicle unable to move after fluid loss; No warning lights prior to failure
Repairs/costs cited: Parts replacement with new OEM hoses.
Recalls/TSBs owners mention: Original OEM hoses discontinued; GM created new replacement hoses. Owner requested recall for all 2020 Sierra trucks.
Engine Knock / Rod Failure
Engine rod failure or bent rods causing severe knocking and requiring engine replacement. Owners report failed engine diagnostics during routine tire installation or early in ownership.
When: Very low mileage: 31,995–86,000 miles; some after only 6 months of ownership
Symptoms owners cite: Sudden loud knocking or rattling from engine; Loss of engine power; Shaking and rough idle; Rod knock sound; White exhaust smoke in some cases
Repairs/costs cited: Full engine replacement. One owner (6.2L, 86K miles) reports rod failure; another (5.3L, 58K miles) experienced engine knock with no prior warning.
Recalls/TSBs owners mention: Recall noted for 6.2L engine; some 2020 models with defective engines acknowledged to have slipped through. GM declined to perform recall or assistance in some cases.
Exhaust Emissions System Failure (P2C7A)
Recurring exhaust emissions system malfunctions with multiple component failures and seven repair attempts since June 2024. Multiple replacements of NOx converter and EGR valve did not resolve issue.
When: Recurring from June 2024 to May 2025 (seventh attempt)
Symptoms owners cite: Check engine light (intermittent or persistent); Exhaust smell; Reduced fuel economy; Limp mode activation (reduces power); OnStar emissions alerts
Codes mentioned: P2C7A (Exhaust Emissions System Failure)
Repairs/costs cited: NOx converter replacement (02/18/25, 03/13/24), EGR valve replacement (02/18/25), multiple diagnostics and repairs. Issue persists after seven attempts.
Recalls/TSBs owners mention: Vehicle inspected by dealer Young Chevrolet-Cadillac multiple times; repairs attempted repeatedly without resolution.
Transmission Shifting Issues (Shuddering, Hesitation, Hard Shifts)
Chronic transmission shuddering, hesitation, or hard shifting at various speeds or during acceleration. Vehicle experiences slip-feel, severe vibrations, and jerking when maintaining speed or accelerating from stops.
When: Starting around 5,000–42,000 miles in some cases; progressive worsening over months
Symptoms owners cite: Shuddering or severe vibration while maintaining speeds over 35 MPH; Hesitation or stuttering on takeoff (especially first start of day); Hard or delayed shifting; Slip-like sensation from transmission or torque converter; Vehicle feels like brakes applied at highway speeds; Jerking during acceleration or deceleration
Repairs/costs cited: Multiple diagnostics often show no codes or fault. Some dealers attribute to torque converter or transmission slip without definitive diagnosis.
Recalls/TSBs owners mention: Several owners report dealers unable to reproduce issue during inspection or claiming no codes found despite symptoms occurring daily.
Dynamic Fuel Management (DFM/AFM) System Failure
Active Fuel Management system failure causing loss of cylinder activation, resulting in bucking, stalling, and rough engine operation. Multiple failed fuel injectors and failed throttle body diagnosed alongside cylinder deactivation failures.
When: Reported at 42,000 miles
Symptoms owners cite: Bucking and stalling during acceleration; Cylinders not activating when called; Rough starting and idle; Numerous noises at various speeds and idle; Loss of power with bucking
Codes mentioned: Check engine light (flashing)
Repairs/costs cited: Failed fuel injectors and throttle body replacement required. Mechanic warned catastrophic failure likely with continued use. New engine recommended over repair.
Recalls/TSBs owners mention: GMC declined assistance. Owner forced to purchase new GM engine at high cost.
Loss of Power / Steering and Brake Assist Failure
Sudden loss of engine power, steering assist, and brake assist while driving, creating immediate safety hazard. Steering wheel hardened and vehicle decelerated uncontrollably on highway exit.
When: Reported while exiting highway and during normal driving
Symptoms owners cite: Sudden complete loss of power; Steering wheel hardened (loss of power steering); Vehicle unable to decelerate normally; Shaking and trembling; Loss of braking assist
Repairs/costs cited: Engine diagnosed as seized; long-term vehicle unavailability.
Recalls/TSBs owners mention: None documented in complaint.
Transmission Shift Solenoid / Selector Issues
Vehicle unable to shift out of park or into drive, neutral, or reverse. Selector lock failure preventing gear selection.
When: Reported on newer models
Symptoms owners cite: Vehicle stuck in park; Unable to shift into drive, neutral, or reverse; Multiple vehicles with same issue reported
Repairs/costs cited: Dealership unable to obtain replacement part; believed to be design flaw requiring part redesign before distribution.
Recalls/TSBs owners mention: GMC unable to send part to dealership. Dealership believes part design defect requires manufacturer redesign.
DEF Tank Heater Failure
Diesel Exhaust Fluid tank heater failure causing emissions warnings and vehicle speed limitation for highway safety. Known issue with no timely repair availability.
When: Reported as known ongoing issue
Symptoms owners cite: DEF emissions warning light (intermittent or persistent); Engine emissions warning light; Vehicle speed limited to unsafe highway speeds while waiting for repair
Repairs/costs cited: DEF tank heater replacement required; repair unavailable for over one month. Not covered by warranty.
Recalls/TSBs owners mention: Known issue acknowledged by GMC service location; no warranty coverage.
Synthesized from 82 NHTSA owner complaints — unverified consumer allegations, summarized for patterns. The verbatim filings appear below.
What owners are reporting 3 most recent
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.…
While driving on the interstate at 70 mph, the transmission began to shudder. It continued the duration of the trip of 90 mins. Following day, the transmission is continuing to shudder and is now shifting hard.
Had powertrain trouble with your 2020 GMC Sierra?
File a complaint with NHTSA → It's free, official, and how every report above got here — owner filings are the federal safety record this page is built on.
Common questions
How serious is the powertrain problem on the 2020 GMC Sierra?
It's a documented issue but not catastrophic. 82 complaints have been filed. Repairs average $2,500 and most owners catch it before it causes a breakdown.
At what mileage does the powertrain typically fail?
Across the 16 complaints that reported odometer mileage, most powertrain failures cluster between 42,000 and 88,000 miles, with the median around 75,450. A quarter of owners report trouble before 42,000; a quarter make it past 88,000. Maintenance history matters more than the odometer alone — this is the reported failure window, not a guarantee.
What does it cost to fix?
Independent shops typically charge around $2,500 for powertrain repairs on this vehicle. Dealer pricing tends to run 20-40% higher. The exact figure depends on the specific failure mode, parts availability, and your local labor rates. If you're outside factory warranty, an extended service contract often covers this category.
Are there any recalls related to powertrain?
No active recalls currently cover powertrain issues on this vehicle. The complaints filed represent owner-reported failures that haven't risen to the level of a manufacturer-issued recall — but they're still worth knowing about before you buy or budget for repairs.
Related
Complaint and recall data sourced from the National Highway Traffic Safety Administration (NHTSA)
public records database. Verify the raw federal record at
nhtsa.gov/vehicle/2020/GMC/Sierra.
Severity ratings are derived from reported crashes, fires, injuries, and fatalities. Repair cost estimates are
independent-shop national averages and may differ in your area. Some links on this page are affiliate links.