2018 GMC Acadia: Transmission & Axle Gear Ratios
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Transmission Gear Ratios
The 2018 GMC Acadia was offered with two automatic transmissions, a 6-speed and a 9-speed.
6-Speed Automatic Transmission (Hydra-Matic 6T70)
| Gear | Ratio |
|---|---|
| 1st | 4.484 |
| 2nd | 2.872 |
| 3rd | 1.842 |
| 4th | 1.414 |
| 5th | 1.000 |
| 6th | 0.742 |
| Reverse | 2.880 |
9-Speed Automatic Transmission (Hydra-Matic 9T65)
| Gear | Ratio |
|---|---|
| 1st | 4.690 |
| 2nd | 3.310 |
| 3rd | 3.010 |
| 4th | 2.450 |
| 5th | 1.920 |
| 6th | 1.450 |
| 7th | 1.000 |
| 8th | 0.750 |
| 9th | 0.620 |
| Reverse | 2.960 |
Available Axle Ratios
| Ratio | Available With | RPO/Axle Code | Best For |
|---|---|---|---|
| 3.87 | 2.5L I4 | GW5 | Fuel Economy |
| 3.16 | 3.6L V6 | G99 | Balanced |
How to Identify Your Axle Ratio
To determine your 2018 GMC Acadia's axle ratio, you can check the Service Parts Identification sticker, also known as the RPO sticker, located in the driver's side door jamb. This sticker contains a list of three-character codes that correspond to the specific options your vehicle was built with. Look for the codes GW5 or G99 in the list to identify your axle ratio.
Alternatively, you can use an online VIN decoder to get a build sheet for your vehicle, which will list the axle ratio among other details.
Towing vs. MPG Impact
A lower numerical axle ratio, such as the 3.16 offered on the V6 models, provides better fuel economy at highway speeds as the engine turns at a lower RPM. A higher numerical axle ratio, like the 3.87 paired with the 4-cylinder engine, is better for towing and acceleration, but at the cost of fuel efficiency.
Common Issues
While the 2018 GMC Acadia is generally a reliable vehicle, some owners have reported issues with the transmission, including rough shifting and transmission failure. The 6-speed automatic transmission in particular has been the subject of a class-action lawsuit for alleged defects. Some owners have also reported issues with the torque converter.
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More specs for the 2018 GMC Acadia
Oil Capacity & Filter
Capacity, weight, filter PN, drain plug torque, change interval.
Fluid Type Specs
Engine oil, coolant, ATF, diff, brake, PS, DEF — with OEM spec numbers.
Coolant Capacity & Type
Total system capacity, OEM coolant spec, flush interval, bleed tips.
Transmission Fluid & Service
Trans model, fluid spec, capacity, filter PN, service interval.
Torque Specifications
Lug nuts, drain plug, caliper, axle nut, plug, key fasteners.
Brake Pad & Rotor Specs
Pad PNs, rotor size, min thickness, caliper torque.
Tire Size & Pressure
OEM size, cold psi, bolt pattern, wheel size, TPMS.
Battery Size & Group
Group size, CCA, AGM/flooded, dimensions, reset note.
A/C Refrigerant & Oil
R-134a or R-1234yf, charge oz, PAG oil spec.
Bulb Sizes (Headlight, Tail, Fog)
Headlight, fog, tail, turn, reverse, interior.
Factory Maintenance Schedule
Service intervals by mileage, severe-duty notes, known issues.
Towing Capacity & Payload
Max tow, payload, GVWR/GCWR, hitch class by trim.
Fuse Box Diagram & Amperage
Fuse box locations, layout, amps, and what each fuse controls.
Serpentine Belt Routing & Length
Belt routing, length, rib count, OEM + aftermarket PNs.
Wheel Alignment Specifications
Camber, caster, toe ranges (front & rear), adjustability notes.
Paint Color Codes
All factory colors with paint codes, sticker location, touch-up tips.
Wiper Blade Sizes
Driver/passenger/rear blade size, attachment, OEM + cross-refs.
Spark Plug Type & Gap
Plug PN, gap, torque, interval by engine.
Key Fob Programming
DIY programming steps, FCC ID, fob PN, battery, transponder.
Same spec — other model years
Maintenance & repair guides
2018 GMC Acadia Maintenance Schedule →
Available maintenance guidance; confirm the manufacturer schedule.
Repair planning references →
Plan the scope of work; detailed procedures need configuration-matched evidence.
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