Thinking about adding the X31 off road package to your GMC Sierra? It’s a big decision, and the internet is full of half-answers. This post breaks down exactly what you get, what it costs, and whether it’s actually worth your money. Stick around — the resale value section alone might change how you think about this option.
What Is the GMC X31 Off-Road Package?
The X31 off road package is GMC’s exclusive off-road equipment bundle for the Sierra lineup. GMC introduced it with the 2019 Sierra redesign as a deliberate split from the Chevrolet Z71 badge. Same hardware, different name — and that distinction matters for brand identity.
Think of X31 as the sweet spot between a base 4WD truck and the full-blown AT4 trim. You get serious traction hardware without a factory lift kit, higher price tag, or awkward step-up height.
It’s available on the Sierra 1500, 2500HD, and 3500HD — but you won’t find it on the Canyon or Yukon.
What’s Actually Included in the X31 Package?
Here’s exactly what you get with the standalone X31 off road package:
- Eaton G80 automatic locking rear differential
- Two-speed Autotrac electronic transfer case (on trims that don’t already have one)
- Off-road tuned Rancho twin-tube shock absorbers
- Stamped steel underbody skid plates
- Heavy-duty high-capacity engine air filter
- Hill Descent Control
- Chrome-tipped dual exhaust (trim dependent)
- X31 exterior badging
- Upgraded all-terrain tires and alloy wheels (varies by trim)
No lift. No drama. Just the gear that actually gets you unstuck.
The Eaton G80: The Star of the Show
If there’s one reason to choose the X31 off road package, it’s the Eaton G80 locking differential.
Standard open differentials send power to whichever wheel spins easiest. Stuck in mud with one wheel on dry ground? The open diff gives all the torque to the slipping tire. You go nowhere.
The G80 — also called the Eaton MLocker — solves this with pure mechanical cleverness. When it detects roughly 100–120 RPM of speed difference between your rear wheels, a flyweight governor fires a pawl that locks both axle shafts together. Both wheels spin at the same speed. Both wheels pull.
The best part? No button. No switch. No thinking. It just works — automatically, in forward and reverse.
Eaton designed it to last up to 300,000 miles on original factory fluid. That’s not a typo.
4-Low Changes Everything Off-Road
The X31 off road package guarantees you get the two-speed Autotrac transfer case. For trucks on lower trims that come standard with a single-speed unit, this is a serious upgrade.
Here’s what the transfer case modes actually do:
- 4-Auto — Senses wheel slip and adds front-axle torque on the fly. Best for mixed wet and dry pavement.
- 4-High — Locks front and rear driveshafts together for continuous traction on snow, gravel, or loose sand.
- 4-Low — Multiplies torque through a secondary planetary gear set. Ideal for steep grades, deep mud, and slow crawling over obstacles.
- Neutral — Disconnects the driveline entirely so you can flat-tow the truck behind a motorhome without pulling driveshafts.
That 4-Low mode paired with the G80 locker? It’s a genuinely powerful combination for serious situations.
Underbody Protection and Air Filtration
The X31 off road package wraps your drivetrain’s most vulnerable parts in stamped steel. A single rock strike to an unprotected oil pan or transfer case can cost you thousands in repairs.
The steel skid plates deflect impacts that a standard truck can’t handle. They’re not cosmetic. They’re functional armor for logging roads, rocky pastures, and anything in between.
The heavy-duty air filter matters too. Off-road environments throw serious dust at your engine. Fine silt and silicates entering the combustion chamber accelerate wear on cylinder walls and piston rings. The X31’s high-capacity air filter uses denser, multi-layered media to catch more of it — which means a healthier engine over the long run.
Hill Descent Control: Smart Braking on Steep Grades
Steep, slippery descents are where drivers get into trouble fast. Stomp the brakes manually and the wheels lock. Locked wheels mean zero steering control.
Hill Descent Control removes that risk. You set a crawl speed, engage the system, and the onboard computer pulses individual brake calipers at each corner faster than any human can. Your tires stay rolling — which keeps you steering.
It’s especially useful on algae-covered boat ramps, icy mountain grades, and steep trail descents. Activate it with a single button below the center stack.
X31 Package Pricing: What You’ll Actually Pay
The X31 off road package comes in two forms:
Standalone X31 Off-Road Package
Includes all the mechanical hardware. On Heavy Duty Sierra 2500HD and 3500HD models, this package starts at around $325 to $440.
X31 Off-Road and Protection Package
Bundles the mechanical upgrades with a factory spray-on bedliner and heavy-duty all-weather floor liners. This one runs $1,400 to $2,665 depending on the model year, trim, and dealer pricing.
For most buyers, the Protection Package delivers better value. The factory bedliner alone retails for $500–$600 at most dealers.
Which Trims Can You Get X31 On?
Not every Sierra trim offers X31. Here’s how it breaks down for the Sierra 1500:
| Sierra Trim | Standalone X31 | X31 + Protection | Notes |
|---|---|---|---|
| Pro | ✅ Available | ❌ Not Available | 4WD required. Not available on Regular Cab Standard Bed. |
| SLE | ✅ Available | ✅ Available | Adds 18-inch machined aluminum wheels + all-terrain tires. |
| Elevation | ✅ Available | ✅ Available | Keeps 20-inch gloss-black wheels. Adds dual exhaust. |
| SLT | ✅ Available | ✅ Available | Upgrades to 20-inch machined aluminum wheels + all-terrain tires. |
| AT4 / AT4X | ❌ Superseded | ❌ Superseded | Off-road features are already standard at a higher spec level. |
| Denali / Denali Ultimate | ❌ Not Available | ❌ Not Available | Luxury-focused trims. Adaptive suspension, no off-road package. |
The AT4 and AT4X trims make the X31 package irrelevant — they already include a factory 2-inch lift, Multimatic DSSV dampers, and mud-terrain tires. The Denali trims prioritize ride comfort and Super Cruise technology over trail capability.
X31 vs. AT4: Which One Do You Actually Need?
The X31 off road package and AT4 serve different buyers.
Choose X31 if you:
- Drive logging roads, construction sites, or boat ramps
- Want off-road capability without a lift
- Care about fuel economy and standard tow ratings
- Plan to aftermarket-upgrade later
Choose AT4 if you:
- Do aggressive trail riding or rock crawling
- Need better approach and departure angles
- Want factory mud-terrain tires and larger mono-tube shocks
- Don’t mind the higher step-in height
The AT4’s factory 2-inch lift improves clearance significantly. But it also raises the center of gravity, affects towing geometry slightly, and adds several thousand dollars to the sticker price. For most weekend warriors, X31 delivers 90% of the capability at a fraction of the cost.
X31 vs. Chevy Z71: Is There Any Difference?
Mechanically? No. The X31 and Z71 use identical hardware — same Eaton G80, same Rancho shocks, same skid plates, same software. The difference is purely branding.
GMC introduced X31 to align with the AT4 and AT4X naming conventions and reinforce its “Professional Grade” identity. If you prefer the GMC badge, you get X31. Chevy loyalists get Z71. Same truck underneath.
The Ride Quality Trade-Off You Should Know About
Here’s an honest heads-up: the X31’s Rancho twin-tube shocks are tuned for off-road use — not highway smoothness.
On paved roads, many Sierra owners report a noticeable “porpoising” effect — a rhythmic bouncing from the rear axle over bumpy asphalt or concrete expansion joints. Because the shocks are valved to drop quickly into ruts and absorb large impacts off-road, they rebound slowly on the highway. With an empty bed, the rear of the truck can feel loose or spongy.
This isn’t a defect. It’s a design compromise.
The popular fix? Swap the factory Rancho shocks for Bilstein 5100s or Fox shocks. Most owners spend under $800 on hardware. The result is a noticeably firmer highway ride with no loss of off-road performance.
The fact that thousands of new truck buyers immediately upgrade the shocks on a brand-new vehicle tells you exactly how valuable the rest of the X31 hardware is.
Engine Pairings: Which Motor Works Best with X31?
The X31 off road package works with every Sierra 1500 engine. Your choice depends on how you use the truck.
| Engine | Horsepower | Torque | Max Towing | Transmission |
|---|---|---|---|---|
| 2.7L TurboMax I4 | 310 hp | 430 lb-ft | 9,400 lbs | 8-Speed Auto |
| 5.3L EcoTec3 V8 | 355 hp | 383 lb-ft | 11,200 lbs | 10-Speed Auto |
| 6.2L EcoTec3 V8 | 420 hp | 460 lb-ft | 13,100 lbs | 10-Speed Auto |
| 3.0L Duramax Diesel | 305 hp | 495 lb-ft | 13,300 lbs | 10-Speed Auto |
Note: Maximum tow ratings frequently require the separate Max Trailering Package.
The 3.0L Duramax diesel is the standout choice for towing to remote locations. Pairing 495 lb-ft of low-RPM torque with the G80 locker makes pulling a heavy boat up a slippery ramp almost effortless.
One thing to watch: if your primary goal is maximum towing capacity, the Max Trailering Package uses stiffer rear springs that conflict with the X31’s off-road suspension tuning. Decide your priority before you configure the truck.
X31 and Resale Value: The Numbers Are Compelling
This is where the X31 off road package really earns its keep.
Factory off-road packages insulate trucks from aggressive depreciation. An X31-equipped Sierra typically holds $2,500 to $4,500 more in resale value compared to an identical truck without it. In the Southwest, Pacific Northwest, and mountain states, demand is even stronger.
X31 trucks also sell 15–20% faster on the used market than standard trucks. That matters if you ever need to sell quickly without cutting your price.
The reason is straightforward: the mechanical components don’t depreciate with the cosmetics. A skid plate on a 100,000-mile truck protects just as well as one on a brand-new truck. The G80 locker fires just as fast on the fifth owner as the first. Used truck buyers know this — and they’ll pay for it.
How to Verify X31 Equipment on a Used Truck
Because X31 adds real money to resale value, fraud happens. Sellers sometimes slap aftermarket X31 stickers on base-model trucks. Don’t get caught out.
Physically check for these:
- Heavy stamped steel skid plates under the front of the truck
- Rancho shocks (red and white labeling) — or aftermarket upgrades like Bilsteins
- Hill Descent Control button on the center stack
- 4-Low position on the transfer case dial
For certainty: run the 17-digit VIN against the original manufacturer build sheet. That document lists every factory-installed option and removes all guesswork.
Is the X31 Off-Road Package Worth It?
For most Sierra buyers — yes, clearly.
The X31 off road package gives you the Eaton G80 locker, two-speed transfer case with 4-Low, steel underbody armor, and Hill Descent Control — all factory-warranted and replicable for far more than the package costs if you tried to source and install each component separately.
The highway ride compromise is real, but fixable with a $700 shock swap. The resale value premium more than covers the initial package cost over time.
If you’re choosing between the X31 off road package and the stock 4WD truck, the mechanical case for X31 is strong. If you’re weighing X31 against the AT4, think honestly about whether you’ll actually be crawling rocks — or mostly navigating muddy farm roads and slippery boat ramps. For the latter, X31 wins on value every time.
