2021 Used GMC Transmissions For Sale

60
verified 2021 GMC transmissions
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Up to 3 yrs
extended warranty available
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shipment

2021 Used GMC Transmissions For Sale

Every 2021 GMC transmission we hold today, sorted by model and by GM option code — 10L80 ten-speeds, 8L90 and 8L45 eight-speeds, 6L80, 6L90 and 6L50 six-speeds, the nine-speed Acadia and Terrain units, and Allison automatics behind the 6.6L Duramax. Shift-tested before shipping and matched to your VIN before you pay.

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Warranty On Every Unit
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Photos Before Shipment
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ASE-Tested & Verified
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Free Nationwide Shipping
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30-Day Money-Back
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Secure SSL Checkout

2021 GMC Transmission Families

Which gearbox sits behind which 2021 GMC, and how many of each we hold today.

Transmission family Fits (2021) In stock
10L80 — 10-Speed Half-Ton Sierra 1500 and Sierra Denali 1500 — 3.0L Duramax, 5.3L Opt MQB, 6.2L (Opt NSS and w/o NSS both held) 10
Allison 1000 — Duramax HD Sierra 2500 HD, 3500 HD, 3500 Pickup and Sierra Denali 2500 — 6.6L L5P Duramax diesel, unit IDs OMCF, OMEF and OMKF 10
10L80 — 10-Speed Full-Size SUV Yukon and Yukon XL 4x4 — 5.3L and 6.2L, Opt MQC, with and without Automatic Engine Stop/Start 8
6.6L L8T Gas HD Automatic — Unit Confirmed by VIN Sierra 2500 HD, 3500 HD, 3500 Pickup and Sierra Denali 2500 — 6.6L gas; these listings carry no option code and GM used more than one automatic behind the L8T, so your VIN settles the unit 6
9T50 / 9T65 — Acadia 9-Speed Acadia 2.5L, 2.0L Turbo AWD/FWD and 3.6L AWD/FWD (2.5L and 2.0L on the 9T50, 3.6L on the 9T65) 5
8L90 — 5.3L Opt MQE 8-Speed Sierra 1500 4x2 and 4x4 and Sierra Denali 1500 4x4 — 5.3L, 8 Speed, Opt MQE 3
6L50 — Canyon 6-Speed Canyon 2.5L 4x4 and 2.8L Duramax 4x2/4x4 — 6 Speed, Opt MYB 3
8L90 — 2.7L Turbo Sierra 1500 4x2 and 4x4 — 2.7L Turbo four 2
6L80 — 5.3L Opt MYC 6-Speed Sierra 1500 4x2 and 4x4 — 5.3L, 6 Speed, Opt MYC 2
6L80 — 4.3L V6 Sierra 1500 4x2 and 4x4 — 4.3L V6 2
8L45 — Canyon 8-Speed Canyon 3.6L 4x2 and 4x4 — 8 Speed, Opt M5T 2
8L90 — Savana 4.3L Savana 2500 and Savana 3500 — 4.3L V6 2
6L90 — Savana 6.6L Savana 2500 and Savana 3500 — 6.6L V8 2
9T45 / 9T50 — Terrain 9-Speed Terrain AWD and FWD automatic 2
5.3L Half-Ton Denali — Unit Confirmed by VIN Sierra Denali 1500 4x2 5.3L; the listing carries no option code and GM shipped that truck with either an 8L90 or a 10L80, so your VIN settles the unit 1
Total 60

Other GMC Model Years

Every model year we hold GMC transmissions for. Years without a link are in stock but have no year page yet — text us your VIN.

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Why Buy a 2021 GMC Transmission from Auto Power Source

2021 is the year GMC's half-ton line ran three different automatics side by side. The same 5.3L V8 left the plant behind a 6L80 six-speed (Opt MYC), an 8L90 eight-speed (Opt MQE) or a 10L80 ten-speed (Opt MQB), and the 6.2L and the 3.0L Duramax both came with the 10L80. Nothing on the outside of the truck tells you which one you have. That is why we match every 2021 unit to your VIN and confirm it in writing before anything is shipped.

All 60 units in this collection are used OEM transmissions pulled from low-mileage donor vehicles, not rebuilds. Each one is inspected, shift-tested on the bench and tagged with its option code or unit ID before it goes on the shelf, so the part you receive is the part the listing describes.

The heavy-duty side is held in depth too. We stock Allison automatics for the 6.6L L5P Duramax across the Sierra 2500 HD, 3500 HD, 3500 Pickup and Sierra Denali 2500 in all three unit IDs — OMCF, OMEF and OMKF — plus the 6.6L gas HD units, which carry no option code in the listing and are matched off the build record instead of guessed at.

Buying a gearbox is mostly a matching problem, and we treat it that way. Text your VIN to +1-307-441-5554 or call 1-877-313-8995 and our ASE-certified team comes back with the exact unit that fits, the price and the transit time in one message — no part-number roulette, and no shipping first and sorting it out later.

📱 Fastest way to match: text us your VIN, get options in minutes.Text Your VIN →

Your 2021 GMC Transmission Options: Compared

Most 2021 GMC owners face four real choices when the transmission fails:

← Swipe sideways to see all columns →
Option Cost Reliability Warranty Fitment Match
Used OEM (this collection) $$$ Best Value High — tested Included VIN-matched
New OEM (dealer) $$$$$ 2-4× more High Manufacturer Exact
Aftermarket / Reman $$$$ Varies 6-12 mo May adapt
Junkyard $ Cheapest Unknown None DIY

Tested used OEM hits the sweet spot — same engineering as new, fraction of the cost.

2021 GMC Transmission Buying Guide

5 things to verify before buying a used 2021 GMC transmission:

  1. Read the option code, not the engine. A 2021 5.3L Sierra can carry a 6L80 (MYC), an 8L90 (MQE) or a 10L80 (MQB). The engine size narrows the field; only the option code closes it.
  2. Check stop/start. Opt NSS marks a truck built without Automatic Engine Stop/Start. The torque converter and calibration differ, so a stop/start unit and a non-stop/start unit are not the same part.
  3. On an HD, match the unit ID. The 6.6L Duramax listings identify the Allison by ID — OMCF, OMEF or OMKF. We hold all three, and the ID has to match your truck, not just the engine and the drivetrain.
  4. Budget for the service parts. Plan on fresh fluid to the correct GM spec, a new filter, a cooler flush and new cooler lines if yours are corroded. A clean install is what makes a used unit last.
  5. Confirm the match with your own VIN before you order. Your VIN settles the transmission code, drivetrain and build split in one step. Text it to +1-307-441-5554 and we will confirm in writing exactly which unit fits your vehicle before you pay.

Our ASE-certified technicians verify every one of these points against your VIN before any unit ships.

📞 Need help choosing the right 2021 GMC transmission? Talk to our team live.Call 1-877-313-8995

Frequently Asked Questions

Will a 2021 GMC transmission from another model fit my truck?
Only if the option code matches. GMC built the 2021 half-ton line with the 6L80, 8L90 and 10L80 depending on engine and option code (MYC, MQE, MQB, MQC), and the cases, bellhousings and control calibrations are not interchangeable between them. Text your VIN to +1-307-441-5554 and we confirm in writing which unit your truck left the factory with.
What is the difference between the 8L90 and the 10L80 in a 2021 Sierra 1500?
The 8L90 is GM's eight-speed and carries option code MQE behind the 5.3L. The 10L80 is the ten-speed and carries MQB on the 5.3L, and it is standard behind the 6.2L and the 3.0L Duramax. They share neither the case nor the valve body, so the swap is not a bolt-in.
Does the 2021 Sierra HD diesel use an Allison?
Yes. The 6.6L L5P Duramax in the 2021 Sierra 2500 HD, 3500 HD, 3500 Pickup and Sierra Denali 2500 runs an Allison automatic, and the listings identify it by unit ID — OMCF, OMEF or OMKF. We hold all three IDs, and the ID has to match your truck.
My 2021 listing says "Gasoline" with no option code. How do you match it?
The 6.6L L8T gas HD listings carry no option code, and GM used more than one automatic behind that engine across this generation. Rather than guess, we read your VIN against the build record and confirm the exact unit in writing before anything ships.
What does Opt NSS mean on a 2021 GMC listing?
NSS is the option code for a truck built without Automatic Engine Stop/Start. It changes the torque converter and the control calibration, so a unit from a stop/start truck and one from a non-stop/start truck are not the same part. We stock both and match it off your VIN.
Is a used 2021 GMC transmission a better buy than a rebuild?
A used OEM unit from a low-mileage donor vehicle is the original GMC part, built to the same spec and tolerances as the one that came out, and it usually costs well under a rebuild. A rebuild depends entirely on who did the work and which parts went back in. Every unit we ship is shift-tested before it leaves.
What warranty comes with a 2021 GMC transmission?
Every unit ships with our standard warranty, and extended coverage is available at checkout. Full terms are on our warranty page, and our team will walk you through what is covered before you order — call 1-877-313-8995 or email info@autopowersource.com.
How fast can a 2021 GMC transmission ship?
Most units in this collection are in stock and ready to leave within one business day of a confirmed order. Freight to a commercial address is the quickest route. Text your VIN and ZIP to +1-307-441-5554 and we will come back with the unit, the price and the transit time together.
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100K+
Engines+Transmissions In Stock
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Our 6-Step Inspection & Shipping Process

Every GMC transmission we ship has been through these six steps:

1. VIN-Matching
We match the donor VIN to your VIN to confirm transmission code, drivetrain, and 2WD/4WD configuration.
2. Tested & Verified
ASE-certified technicians Shift-Test every gear under load. Units are checked for clean engagement, no slipping, no abnormal noises.
3. Noise & Smoke Verification
Units are run to verify normal mechanical sound and clean operation — catches internal wear static tests miss.
4. Visual Inspection
Every accessible component is inspected: bell housing, output shaft, solenoid pack, cooler lines, sensor harnesses.
5. Photograph & Catalog
Multi-angle photos sent to you BEFORE we ship for your approval.
6. Palletize & Ship
Strapped on a heavy-duty wooden pallet, shipped via freight at no charge.

Our Photos-Before-Shipment Guarantee

Before any transmission leaves our warehouse, we send you multi-angle photographs. You approve. If you do not approve, you get every dollar back — no questions, no restocking fees, no return freight charges. On top of 30-day money-back and the warranty included with every unit. Browse all 60 2021 GMC transmissions below.

✉ Email Us at info@autopowersource.com
No match? Text VIN →