Back to 2021 GMC Sierra 3500HD
Help
2021 GMC SIERRA 3500HD
6.6L V8 L8T•4WD•AUTOMATIC•gas•turbo
Founding sponsor spot is openYour name on every procedure for this vehicle, permanently.Sponsor — $99 →
Repairs0Labor507Torque3518Fluid10DTC1253Battery1Maintenance0Recalls0
Fluid · Automatic Transmission

Automatic Transmission

for 2021 GMC Sierra 3500HD 6.6L V8 L8T · 4WD
Fluid Type
Dexron VI ATF
Spec: GM Dexron VI
Capacity
16.9qt
15.99 L
Drain & Refill
5 qt
4.73 L
Change Interval
50,000 mi
80,450 km

Notes

6L90 6-speed automatic. Full capacity includes torque converter. Standard drain-and-fill service amount is approximate.

Buy on Amazon
As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Other fluid systems on this vehicle

🔌 Need this data in your app? It's all in the free API →
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Mechanic · 20+ years. Spot an error? Use the Help link above — a human reads every report.
Stuck on this repair? Take it to The Diag Desk — ask a master tech about this exact car → real human answer within 24h, never AI
Share:XRedditFBWhatsAppThreadsEmail
⚠ STILL BEHIND THE PAYWALL
The 2021 GMC Sierra 3500HD repair data is incomplete because no one has sponsored it yet. For $99, we generate the full step-by-step procedures, then fact-check them with a second AI pass and your expert review. Your name on every procedure, permanently.
The same data would cost $169/mo from Mitchell1 or $30/year from ALLDATAdiy — and you'd be renting access, not freeing it. Sponsor once, free forever.
Sponsor the GMC Sierra 3500HD — $99 →
Building an app?
Free API access to all this data — 10 requests/day, no card required.
Get an API key →
Run a shop?
Manage repairs, estimates, and customers with ShopBase — $249/mo, all features included.
Try ShopBase →