How much transmission fluid does a 2020 GMC Sierra 2500HD take?

10.5 quarts as a total fill for the 6L90 transmission (10.5 to 22.1 quarts across this year's engines). A drain-and-refill without removing the pan replaces roughly a third to half of that, so refill to the level check point rather than pouring in the whole figure.

What transmission fluid does a 2020 GMC Sierra 2500HD use?

The source names WSS-M2C949-A for this year. Use a fluid that states that specification on the bottle.

What brake fluid does a 2020 GMC Sierra 2500HD take?

Check the brake fluid reservoir cap - it states the DOT grade. DOT 3 and DOT 4 can be mixed; DOT 5 silicone fluid cannot.

2020 GMC Sierra 2500HD transmission fluid capacity and fluid specs

GarageDex's fluid data shows the 2020 GMC Sierra 2500HD (6.6L 8-cyl) uses the 6L90 automatic transmission, which holds 10.5 quarts of fluid as a total fill. Other engines on this year hold 10.5 to 22.1 quarts - see the table.

Shop WSS-M2C949-A fluid Match the specification on the bottle to your manual

Key takeaways

Transmission: 6L90 automatic transmission, 10.5 qt total fill.
Total fill is the whole system; a drain-and-refill takes a third to half.
Brake fluid grade: read it off the reservoir cap.
The fluid specification is named by the source - buy a fluid that lists it.

2020 GMC Sierra 2500HD fluids by engine
Engine	Transmission	Total fill	Fluid spec	Brake fluid	Gear oil
6.6L 8-cyl	6L90 automatic	10.5 qt	per owner's manual	see reservoir cap	rear 3.15 qt front 1.9 qt transfer case 1.6 qt
6.6L 8-cyl	10L1000 automatic	22.1 qt	WSS-M2C949-A	see reservoir cap	rear 3.15 qt front 1.9 qt transfer case 2.45 qt

Fluids for the 2020 GMC Sierra 2500HD

Buy fluid that states the specification your manual names. Multi-vehicle fluids list the specs they meet on the back label - if yours is not listed, it is the wrong bottle.

WSS-M2C949-A fluidYou need about 11 quarts for a full fillShop fluid DOT 3 or DOT 4 brake fluidA quart covers a full flushShop brake fluid Fluid transfer pumpMost modern transmissions have no dipstick tube - you fill from belowShop pumps

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Other 2020 GMC Sierra 2500HD specs

All specs Engine oil Coolant capacity Maintenance schedule

Other Sierra 2500HD years

2026 2025 2024 2023 2022 2021 2019

Source: AMSOIL Auto & Light Truck lookup. Capacities are total system fills; a drain-and-refill takes less. Where no fluid specification is shown, the source lists only a catalog code, so use the specification printed in your owner's manual - the wrong transmission fluid damages a transmission.