A complete pickup truck or SUV driveline service covers three separate fluid sumps, and none of the three share a fluid with the others: the transfer case takes its own OEM-specified product, the front differential takes a second specification, and the rear differential takes a third. American Oil Wholesale and Distribution (aoilw.com), a Hialeah-based full-line distributor, stocks API GL-5 gear oil by the pail and drum for both differential sumps, plus Dexron VI ATF and ATF+4 for the transfer case applications where those grades are specified.
South Florida runs a heavy mix of work trucks and recreational SUVs. A Doral logistics company servicing a fleet of F-series SuperDuties, a Homestead landscaper with a RAM 2500, or a weekend boat-tower keeping a Silverado ready for the water, all need a bay that has the right fluid for the right sump. Stocking a single gear oil and assuming it covers all three compartments is one of the most reliable ways to create a comeback in a truck bay. This guide maps the three sumps, what each one takes, and how a South Florida shop can stock them without overstocking.
Why the three sumps are not interchangeable
Modern 4x4 and AWD trucks and SUVs have up to three separate driveline fluid sumps, each sealed independently:
- The transfer case splits torque between the front and rear axles.
- The front differential distributes torque between the front wheels.
- The rear differential distributes torque between the rear wheels.
Each was engineered with different load, thermal, and friction-modifier requirements. A transfer case spec is not the same as a rear differential spec even on the same truck, and using one fluid across two of these compartments risks premature wear or seal damage. The OEM service data is the authority; the fluid label alone is not.
Transfer case fluid: the most variable spec
The transfer case is where the most shops make the wrong substitution, because the spec varies more widely by OEM and generation than any other driveline compartment:
- General Motors (Silverado, Sierra, Tahoe, Suburban): GM transfer case fluid specifications changed with platform generation. Older trucks from approximately 1998 through the mid-2000s, equipped with BorgWarner-style automatic transfer cases, specified AutoTrak II. Later platforms transitioned to Dexron VI ATF for the transfer case. Confirm the model year, transfer case type, and OEM service data before filling.
- Ford (F-150, F-250/F-350, Expedition): Ford specifies Motorcraft Mercon LV (XT-10-QLVC), a full synthetic Mercon-type ATF, for the BorgWarner transfer cases in current F-series trucks. Using incompatible grades such as Mercon V, Dexron III, or generic ATF is outside Ford's service specification and can damage clutch packs and seals. Verify the application in Ford's service data for the specific model year.
- RAM/Stellantis (RAM 1500, RAM 2500/3500): RAM transfer case fluid requirements vary by platform and generation. BorgWarner transfer cases in current-generation RAM trucks require Mopar BW transfer case fluid; ATF+4 is not an approved substitute in those units. Older RAM trucks with NV-series transfer cases specified ATF+4. Confirm which transfer case is installed, and the correct fluid, from the OEM service data.
- Toyota (4Runner, Tundra, Tacoma): Toyota specifies a Toyota-specific transfer case fluid depending on the model and generation. Newer models use a dedicated fluid distinct from Toyota's general ATF grades. The OEM service data identifies the current specification.
The consistent rule: the transfer case spec varies by OEM and generation and is not interchangeable with a neighboring differential fluid. Some OEMs specify an ATF; others specify a dedicated transfer case fluid. Either way, the spec must come from the OEM service data, not from the shelf next to the truck.
Front differential fluid
In a 4x4 truck or SUV, the front differential commonly takes one of:
- API GL-5 gear oil (SAE J306 viscosity grade, typically 75W-90 or 80W-90): the most common spec for solid front axle differentials on domestic and Japanese trucks.
- OEM-specific gear oil: some IFS front axles, common on GM and Toyota trucks, specify an OEM-grade gear oil rather than standard GL-5. The differential housing spec on IFS trucks is separate from the transfer case spec on the same vehicle.
The OEM service data is the authority. Confirm the front differential spec and the transfer case spec independently; they are different sumps with different requirements even on the same truck.
Rear differential fluid
API GL-5 75W-90 or 80W-90 covers most conventional rear differentials in domestic and Japanese trucks. The American Petroleum Institute defines the GL-5 service category for hypoid axle gear lubricants under high-load conditions; SAE J306 sets the viscosity windows. 75W-90 covers the vast majority of light-duty rear axles; 80W-90 is the traditional alternative for the same load range.
Limited-slip differentials require a friction modifier additive. Most GL-5 gear oils do not include this modifier at the concentration a limited-slip unit needs. A separate LS friction modifier concentrate is blended in at fill, per the additive's dosing specification and the OEM requirement. Skipping it in a limited-slip rear end causes clutch-pack chatter on turns.
Heavy-duty rear axles under sustained towing loads can require 80W-140, a heavier SAE J306 grade. Check the OEM service data for the specific axle and duty cycle. South Florida's ambient heat reinforces why compliance with the correct heavy-duty spec matters: NOAA records a Miami-Dade County average July high of 91 degrees F (33 degrees C), and a truck towing a boat through Homestead traffic all afternoon runs its rear axle hotter than the same truck in a cooler climate. 80W-140 provides a thicker protective film at those elevated sump temperatures.
South Florida stocking guide
Florida consistently ranks among the top states for pickup truck registrations, and the South Florida mix leans heavily toward domestic brands, with Toyota and Nissan significant in the mid-size segment. A South Florida auto shop with a busy truck bay can cover the majority of its driveline work with four SKUs:
| Product | What it covers | Package |
|---|---|---|
| American Oil GL-5 80W-90 | Rear and solid front differentials on most domestic and Japanese light-duty trucks | Pail (5 gal) or drum (55 gal) |
| American Oil GL-5 80W-140 | Heavy-duty rear axles on HD trucks; sustained towing loads | Pail (5 gal) or drum (55 gal) |
| American Oil Full Synthetic Dexron VI ATF | Transfer cases on later-generation GM trucks where Dexron VI is specified | Pail or drum |
| American Oil ATF+4 | Transfer cases on older RAM trucks with NV-series transfer cases (ATF+4 spec) | Pail or drum |
We carry American Oil GL-5 gear oil in drum (55-gallon, approximately 220 quarts) and pail (5-gallon) format at account pricing, so a busy truck bay can move to the drum and cut its per-quart cost on the gear oil grades it turns fastest.
Ford BorgWarner transfer cases require Motorcraft Mercon LV (XT-10-QLVC) and current-generation RAM BorgWarner units require Mopar BW transfer case fluid; both are OEM-proprietary and should be sourced from your Ford or Stellantis dealer. Limited-slip friction modifier concentrate is not stocked by American Oil; source it from an OEM dealer or aftermarket supplier.
Caribbean and Latin America export
The API GL-5 service category and the SAE J306 viscosity grades are internationally recognized, so the same drum of gear oil that services a South Florida truck works for export accounts in the Caribbean and Latin America. Pickup truck populations in the Caribbean and Central America skew older and run the same axle specs as their domestic counterparts. We export by freight forwarding and container loading from the Miami gateway, and GL-5 gear oil in drums ships well for distributor accounts in Kingston, San Juan, and Santo Domingo.
Open a wholesale account with American Oil
Open your wholesale account at aoilw.com, or call American Oil Wholesale and Distribution, and put GL-5 80W-90 and 80W-140 gear oil for your differentials, Dexron VI ATF for later-generation GM trucks, and ATF+4 for older NV-series RAM trucks on one invoice. Delivery from Palm Beach County to Homestead; Caribbean and Latin America export available. We offer COD terms, so a new account can start clean before longer credit terms are arranged. Tell us the truck mix your bay sees most and request a wholesale quote.
Sources
- American Petroleum Institute (API), gear lubricant service categories including GL-5. https://www.api.org
- SAE International, SAE J306 automotive gear lubricant viscosity classification. https://www.sae.org
- NOAA National Centers for Environmental Information, Miami-Dade County monthly climate normals. https://www.ncei.noaa.gov
- General Motors, AutoTrak II transfer case fluid specification (GM owner's manual and service data).
- Ford Motor Company, Motorcraft Mercon LV transfer case fluid specification (Ford owner's manual and service data; part number XT-10-QLVC).
- Toyota Motor Corporation, transfer case fluid specification (Toyota owner's manual and OEM service data by model and year).
