2016 GMC Sierra Transmission Fluid Change Guide

The 2016 GMC Sierra runs the GM 6L80 6-speed automatic transmission. This is a robust, well-built transmission — but it shares one vulnerability with every other automatic: degraded fluid. Changing the transmission fluid yourself saves $250–$350 and takes about an hour.

What You'll Need

• Fluid: ACDelco 10-9395 Dexron VI ATF or equivalent full-synthetic Dexron VI
• T27 Torx or 3/8" ratchet (pan bolts), 15mm socket (drain plug if equipped)
• Fluid transfer pump, drain pan (7-quart capacity)
• New 6L80 pan gasket (GM part number 24236931)
• Torque wrench, shop rags

Dexron VI capacity:

• Drain-and-fill: approximately 4.0–5.0 quarts
• Pan service: approximately 6.0–7.0 quarts refill
• Total 6L80 system: ~11.4 quarts (never exchanged all in one service)

Drain-and-Fill vs. Flush

My recommendation: Drop the pan, replace the filter and gasket, refill with Dexron VI. This exchanges 50–60% of total fluid, allows pan debris inspection, and is safe for any mileage transmission. Do NOT machine-flush a high-mileage 6L80 — the fresh fluid can dislodge deposits acting as informal seals.

Step-by-Step

1. Warm the transmission — Drive 10–15 minutes.
2. Raise and support on jack stands.
3. Check for drain plug — Some 6L80 Sierras have a 15mm pan drain plug. Use it if present — much cleaner than pan drop.
4. Drop the pan — Loosen front/side bolts first, leave rear bolts partially in. Let front drop to drain before removing fully.
5. Inspect pan debris — Fine metallic powder: normal. Chunks of metal or fibrous clutch material: get professional assessment.
6. Remove the old filter — Snap-fit into valve body. Pull straight down.
7. Install new filter — Press up until it snaps.
8. Clean pan surfaces — All old gasket material off.
9. Install new gasket and pan — Torque pan bolts to 97 in-lbs (11 Nm) in crisscross pattern.
10. Add Dexron VI — Through fill tube. Start with 5 quarts.
11. Cycle shifter — P-R-N-D-3-2-1-P with engine at idle, then recheck fluid level at operating temperature (175–195°F).

Troubleshooting

ATF leak from pan: Check torque — more than 97 in-lbs warps aluminum pans. Verify gasket isn't pinched.

Delayed engagement after service: Normal initially. If shifts are harsh after 50 miles, check fluid level at operating temp.

Final Thoughts

The 6L80 in your 2016 GMC Sierra rewards proper maintenance. Drop the pan every 50,000 miles, Dexron VI only, 97 in-lbs on the pan bolts. For more Sierra DIY guides, browse all articles at /blog or access the full library with an OwnerDrop Starter plan at $29.99/mo.