GMC TruckSierra 3500 HD2021Overview/gmc-truck/sierra-3500-hd/2021/base/

2021 GMC Truck Sierra 3500 HD

Factory specifications, fluid capacities, torque values, EPA fuel economy and the federal safety record for the 2021 Sierra 3500 HD.

The 2021 GMC Sierra 3500 HD is a heavy-duty full-size pickup built for demanding towing and hauling applications, and it carries a 10.0-quart engine oil capacity with a 15W-40 viscosity recommendation. That model year recorded 20 owner complaints, with Power Train issues representing the most frequent concern, alongside five safety recalls issued for the vehicle. When viewed against the Sierra HD's broader complaint history from 1999 through the projected 2026 timeframe—where 2014 saw the highest volume at 108 complaints and 2001 the lowest at just 1—the 2021 falls notably below the historical peak, positioning it as a relatively more stable iteration within the model's long-term reliability trajectory.

Model year2024202220212019

Quick specs

Fluid capacities, tune-up values and fuel economy at a glance.

Engine oil capacity10.0 qtOEM · verified
Engine oil type15W-40OEM · verified
Lug nut torque140 ft-lbsOEM · verified

Fitment & sizes

Replacement part sizes and factory part numbers — battery, bulbs, filters and belts.

From the factory this vehicle uses a BCI Gas: 94R; Diesel: 2 Batteries: 48; Auxiliary: 48 · Gas: 720; Diesel: 2 Batteries: 730; Auxiliary: 730 CCA battery, OE oil filter 12684038. Each part links to every other vehicle that shares it, so a part you already stock may fit more of your fleet than you'd expect.

Battery groupBCI Gas: 94R; Diesel: 2 Batteries: 48; Auxiliary: 48 · Gas: 720; Diesel: 2 Batteries: 730; Auxiliary: 730 CCAOEM · verified
Tire sizeLT275/70R18/E 125/122SOEM · verified
Wheel / rim8, DRW: 6.5 inOEM · verified

OE service part numbers OEM · verified

Engine oil filter12684038 alt 12731742
Engine air filter84121219 alt 84554703
Fuel filter13539108
Spark plug12622441
Battery88865934 alt 88866309
Front wiper blades84578275
Serpentine belt12658178 alt 12732707
Thermostat12680544 alt 89018168
Cabin air filter13508023

Service quick specs OEM factory data

Capacities, torques and tune-up values from the factory service manual.

This engine holds 10.0 qt of 15W-40 engine oil, Dot 3 brake fluid. Torque lug nuts to 140 ft-lbs. The firing order is 1-2-7-8-4-5-6-3.

Lubricants & capacities

Automatic Transmission FluidATF
Automatic Transmission Fluid Capacity14.37 qt
Automatic Transmission FluidATF
Automatic Transmission Fluid Capacity6.0 qt
Brake FluidDot 3
Brake Fluid Capacity2.11 pt
Engine Coolant Capacity30.1 qt
Engine Coolant Capacity15.5 qt

Engine torques

Crankshaft Position (CKP) Sensor Bolt(s)7.4 ft-lbs
Camshaft Position (CMP) Sensor Bolt(s)7.4 ft-lbs
Crankshaft Position (CKP) Sensor Bolt(s)18.0 ft-lbs
Camshaft Position (CMP) Sensor Bolt(s)18.0 ft-lbs
Engine Coolant Temperature (ECT) Sensor Bolt(s)24.0 ft-lbs
Engine Coolant Temperature (ECT) Sensor Bolt(s)15.0 ft-lbs
Oxygen (O2S) Sensor Bolt(s)31.0 ft-lbs
Knock Sense (KS) Bolt(s)18.0 ft-lbs

Chassis torques

Lug Nuts140 ft-lbs
Transfer Case Fill Plug15.0 ft-lbs
Transfer Case Drain Plug15.0 ft-lbs

Ignition

Cylinder Firing Order1-8-7-2-6-5-4-3
Cylinder Firing Order1-2-7-8-4-5-6-3
Spark Plug ManufacturerAC Delco
Spark Plug Gap.037-.043 in
Spark Plug Torque15 ft-lbs

Battery & A/C

RefrigerantR134a
Refrigerant Capacity1.40 lbs
Oil GroupPAG
Oil Capacity3.40 oz

Brakes

Brake Caliper Bolt to Carrier Torque55.0 ft-lbs
Brake Caliper Carrier to Hub Bolt Torque221.0 ft-lbs
ABS Sensor Torque6.7
Vented Rotor Minimum Thickness for ReplacementFront: 1.516
Vented Rotor Minimum Thickness after RefinishFront: 1.535
Variation from Parallelism Thickness Variation.001"
Maximum Rotor Runout.002"

Multi-step torque procedures OEM · verified

Front Wheel Hub — tightening sequence 1 stages

Prep Use a new retaining nut. Driveshaft Nut: Step 1: 244.0 ft. lbs., Step 2: Loosen 45°

3199.0
Connecting Rod (Large End) Bearings — tightening sequence 1 stages
126.0 ft. lbs., Step 2: 30°, Step 3: 30°, Step 4: 30°26 ft. lbs
Connecting Rod (Large End) Bearings — tightening sequence 1 stages
115.0 ft. lbs., Step 2: 85°15 ft. lbs
Cylinder Head — tightening sequence 1 stages
159.0 ft. lbs., Step 2: 90°, Step 3: Internal Short Hex Bolt: 40°, Step 4: All Except Internal Short Hex Bolt: 60°59 ft. lbs
Cylinder Head — tightening sequence 1 stages
159.0 ft. lbs., Step 2: 90°, Step 3: Internal Short Hex Bolt: 40°, Step 4: All Except Internal Short Hex Bolt: 60°59 ft. lbs
Cylinder Head — tightening sequence 1 stages
122.0 ft. lbs., Step 2: 59.0 ft. lbs., Step 3: 120°, Step 4: 24.0 ft. lbs.22 ft. lbs
Flex or Driveplate Bolts — tightening sequence 1 stages
111.0 ft. lbs., Step 2: 22.0 ft. lbs., Step 3: 45°11 ft. lbs
Engine Flywheel Bolts — tightening sequence 1 stages
159.0 ft. lbs., Step 2: 60°, Step 3: 60°59 ft. lbs

Factory maintenance schedule OEM · verified

Normal service, condensed from the factory interval matrix.

Under the factory schedule, replace the spark plugs every 97,500 mi; coolant at 150,000 mi. The big-interval services (at 150,000 mi for coolant, and the transmission fluid) are the ones owners most often skip — on a lower-mileage example, assume the original fluids are still in it and check them first.

Every 7,500 miAccelerator Pedal (inspect) · Body Latches, Locks & Hinges (lubricate) · Brake Shift Interlock Solenoid (inspect) · Brake System (inspect) · CV Joint Boot (inspect) · Engine Air Filter Element (inspect)
Every 15,000 miWindshield Wiper Blade (replace)
Every 22,500 miCabin Air Filter (replace) · Fuel Filter (replace)
Every 45,000 miEngine Air Filter Element (replace) · Fuel Evaporative Emission Control System (inspect)
Every 75,000 miHood Hinge (inspect)
Every 97,500 miSpark Plug Wires (inspect) · Spark Plugs (replace) · Transfer Case Assembly (drain & refill)
At 150,000 miAccessory Drive Belt (inspect) · Engine Coolant System (drain, flush & refill)

Reliability & federal safety record

Owner-reported issues, recalls, investigations and service bulletins on record with NHTSA — an unfiltered look at what owners actually experience.

Owner complaints about the 2021 GMC Truck Sierra 3500 HD lead in one area — the power train, 5 of 20 reports (25%), well ahead of the next concern. That matters, because the power train are also the target of recall 21V-758 on this vehicle — so the single most useful check before buying or servicing one is confirming it was actually performed. 0 of the reports describe a crash and 0 a fire — a small share of the total, but worth weighing against the power train pattern above. These are tallies of what owners actually reported to the federal government, not an editorial score — and higher-selling models naturally rack up more reports.

5
Open recalls
NHTSA campaigns
833
Service bulletins
Manufacturer communications
1
ODI investigations
Office of Defects Investigation
20
Owner complaints
0 involved a crash · 0 a fire
Owner complaints by model year NHTSA · this generation & adjacent

Owner complaints filed with NHTSA, by component

All 20 complaints on record, top 8 components.

Power Train5
Service Brakes3
Unknown Or Other2
Electrical System,Visibility1
Back Over Prevention1
Electrical System1
Electrical System,Unknown Or Other,Engine1
Tires1

Source: NHTSA Office of Defects Investigation complaint database.

Recalls NHTSA · verified

Showing 2 of 5 campaigns on record for this vehicle.

21V758000Service Brakes, Hydraulic:Power Assist:Electric:Control ModuleReported 29/09/2021

General Motors, LLC (GM) is recalling certain 2021-2022 Chevrolet Silverado 2500, Silverado 3500, GMC Sierra 2500, and Sierra 3500 vehicles with electronic brake control modules (EBCM) replaced during vehicle assembly… Remedy: Owners are advised to park outside and away from other structures until the recall repair is completed. Dealers will replace the BPMV assembly, free of charge. Owner notification…

20V792000Seat BeltsReported 17/12/2020

General Motors, LLC (GM) is recalling certain 2019-2021 Chevrolet Silverado 1500 and GMC Sierra 1500, 2021 Chevrolet Suburban and Tahoe and GMC Yukon XL and 2020-2021 Chevrolet Silverado 2500 and 3500 and GMC Sierra… Remedy: GM will notify owners, and dealers will inspect left-side and right-side front-row center seat-belt bracket attachments and reassemble it correctly as necessary, free of charge…

Technical service bulletins NHTSA · verified

Showing 5 of 833 bulletins on record with NHTSA.

BulletinDateComponentSummary
PIT6473F2026-07-17Unknown Or OtherThis PI was created to help avoid unnecessary front camera module replacements
PIT65322026-07-06Unknown Or OtherThe purpose of this PI is to inform dealer technicians of a normal cab pressure relief…
PIT5544J2026-06-24Unknown Or OtherThis Preliminary information communicates information on a hydraulic rush type noise from…
PIT5966F2026-06-23Unknown Or OtherThis Preliminary information communicates an issue with an OTA pending message still…
PIT65232026-06-10Unknown Or OtherThis PI provides diagnostic steps for dealer technicians to verify the condition and…

Common OBD-II trouble codes

The most common OBD-II codes for this vehicle's emissions system. These are standardized SAE J2012 definitions, not vehicle-specific fault reports.

P0420
Catalyst system efficiency below threshold — Bank 1
P0300
Random / multiple cylinder misfire detected
P0171
System too lean — Bank 1
P0455
Evaporative emission system leak detected — large leak
P0128
Coolant thermostat below regulating temperature
P0442
Evaporative emission system leak detected — small leak

VIN tools

Decode factory build data for a specific vehicle by VIN.

VIN
Decode a VIN to confirm the transmission and build data for a specific Sierra 3500 HD. OEM
Build data
Plant, GVWR class, engine and body data for any 17-character VIN.
Recalls
Check open recall campaigns against a specific vehicle by VIN.

Vehicles with shared specs

Find every vehicle that shares this one's battery, bulbs, oil capacity, platform or parts.

Reference guides

Cross-vehicle references for the kinds of data on this page.

Frequently asked

How much oil does the 2021 Sierra 3500 HD take?

10.0 qt of 15W-40, per the factory manual.

Does the 2021 Sierra 3500 HD have open recalls?

NHTSA lists 5 recall campaign(s) for this model year. Check your specific vehicle by VIN.