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GM Auto Trak II is a specialized fluid built specifically for clutch-on-demand systems in GM Autotrac four-wheel-drive transfer cases. It is not interchangeable with regular automatic transmission fluid (ATF).
ACDelco GM Original Equipment 10-4017 Auto-Trak II Transfer Case Fluid
Auto Trak II contains friction modifiers, detergents, and thermal stabilizers that standard ATF does not have. These additives are what allow the clutch packs inside the transfer case to engage and disengage smoothly during automatic 4WD operation. Without them, you get shuddering, premature wear, and potential damage.
Alternatives to GM Auto Trak II Transfer Case Fluid
The current ACDelco part numbers are GM Part #88900402 and ACDelco Part #10-4017. Earlier listings used GM Part #12378508 or GM Part #12378261.
Royal Purple Synchromax
Royal Purple-ROY01512 ROYAL PURPLE SYNCHROMAX QT. TRANSFLUID
Royal Purple Synchromax is a full synthetic manual transmission and transfer case fluid. It is one of the more commonly recommended aftermarket equivalents for GM Auto Trak II. It is built for drivetrains that specify ATF or a light-viscosity lubricant but need more protection than standard ATF provides.
Quick Specs
- Viscosity @ 40°C: 39 cSt
- Viscosity @ 100°C: 7.5 cSt
- Viscosity Index: 162
- Pour Point: -51°C (-60°F)
- Flash Point: 207°C (405°F)
- 4-Ball Wear Scar: 0.34 mm
The fluid uses Royal Purple’s Synerlec additive technology, which improves film strength and reduces metal-to-metal contact. This protects components in Autotrac transfer cases where the clutch packs run hot and without a dedicated cooler.
Synchromax also protects brass and bronze components found in synchronizers, conditions seals, and flows reliably in cold temperatures.
Owners report noticeable improvements after switching, including smoother shifts, quieter operation, and resolved gear grind in 1st-to-2nd transitions at high RPM. In transfer case use, owners noted smoother mode transitions.
This is a good fit for owners outside of their powertrain warranty who want a proven synthetic alternative at a lower price than OEM.
Also compatible with:
- Manual transmissions specifying ATF or light-viscosity fluid
- Off-road motorcycle and ATV transmissions with a separate transmission sump
- Ford XL-12 transfer case applications
Valvoline Transfer Case Fluid (TCF)
Valvoline Multi-Vehicle (TCF) Conventional Transfer Case Fluid
Valvoline Transfer Case Fluid is an aftermarket equivalent for GM Auto Trak II, explicitly listed by Valvoline for use in GM Autotrac transfer cases.
It is formulated for chain-driven transfer cases in full-size and compact trucks and SUVs, making it a practical, widely available option for GMT800 and GMT360 owners outside of their powertrain warranty.
Quick Specs
- Viscosity @ 40°C: 28.82 cSt
- Viscosity @ 100°C: 5.91 cSt
- Viscosity Index: 156
- Pour Point (Brookfield @ -40°C): 10,200 cP
- Flash Point: 202°C
- Color: Red
Where standard ATF falls short in Autotrac systems, this fluid is specifically formulated with the friction modifiers, seal conditioners, and oxidation resistance these transfer cases need.
One owner reported that after an initial change where the old fluid came out black, a follow-up change showed the fluid holding a healthy dark red, suggesting it cleaned the internals effectively.
Customers report noticeably smoother 4WD engagement, quieter transfer case operation, and in at least one GMT360 case, a dashboard indicator light that stopped cycling after the switch. One Range Rover owner reported zero issues over 30,000 miles using it as an Auto Trak II substitute.
Also compatible with:
- Ford XL-12 transfer cases
- Transfer cases specifying Dex/Merc or ATF+4 fluid
Why There Are Only Few Alternatives to GM Auto Trak II
Auto Trak II is not a standard automatic transmission fluid. It is a specialized lubricant built for the wet clutch pack inside GM’s Autotrac clutch-on-demand transfer cases, including the NP8, NV246, and NVG 226 HD.
In Auto 4WD mode, the transfer case computer continuously engages and slips the internal clutch pack to manage traction. This happens constantly, under load, and without a dedicated cooler to shed heat. Standard ATF, including Dexron III and Dexron VI, was not designed for this kind of sustained mechanical stress; and does not provide the friction behavior these clutches need. Use the wrong fluid and you get shuddering, binding in tight turns, or a failed transfer case.
This is also why heavy-duty trucks like the 2500HD and 3500, along with older manual-shift 4WD vehicles, can run regular ATF. Those systems do not have the automatic clutch engagement function, so they do not need the specialized friction modifiers.
Auto-Trak II starts with a Dexron III base but carries a high concentration of friction modifiers that calibrate the exact slip-and-grip behavior the clutch pack requires.
Beyond that, a transfer case fluid handles heat without a cooler, conditions the seals specific to Autotrac systems to prevent leaks, maintains a strong lubricating film under load to protect chains, bearings, and planetary gears, and flows consistently in cold temperatures to prevent whining or stiff cold-start engagement.
To protect your 4WD system from unnecessary wear, it helps to understand why transfer case fluid matters and how its unique chemistry supports your vehicle.
Which Vehicles Use Auto-Trak II
Auto Trak II is required for Autotrac transfer cases, including the NP8, NV246, NP246, BW4482, and NVG 226 HD. You will find these in full-size GM trucks and SUVs from the GMT800 platform, which includes the Silverado, Sierra, Tahoe, and Yukon.
The GMT360 platform vehicles, including the TrailBlazer and Envoy, also use Auto Trak II. If you drive one of these trucks, the Chevy 5.3 oil capacity and oil type guide is a useful read while you are already thinking about maintenance.
Most experts recommend changing Auto Trak II every 45,000 to 60,000 miles under normal driving conditions. If your vehicle sees severe use, such as frequent towing, regular off-roading, or extended 4WD operation, shorten that interval to every 30,000 to 40,000 miles.
Closing Notes
If your vehicle is still under its powertrain warranty, use ACDelco Auto Trak II (GM Part #88900402). These transfer cases are sensitive, and the OEM fluid removes any question about whether the right friction and thermal properties were maintained.
The price difference over an aftermarket option is small compared to the cost of a transfer case replacement.
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