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4WD and AWD both drive all four wheels. They differ in two ways that matter: whether front and rear can turn at different speeds (so the system can stay engaged on dry pavement), and whether a low-range gear set is available for slow, steep or technical ground. Badges don't tell you either one. The spec sheet does.
At a Glance
| System type | Can stay engaged on dry pavement? | Low range? | Example |
|---|---|---|---|
| Part-time 4WD | No, only on loose or slippery surfaces | Yes | Jeep Command-Trac (2.72:1) |
| Full-time 4WD | Yes | Yes | Jeep Selec-Trac (2.72:1), full-time Rock-Trac (4.0:1) |
| Full-time AWD | Yes | No | Subaru Symmetrical AWD, Jeep Quadra-Trac I |
| On-demand (part-time) AWD | Yes | Usually no | Front- or rear-drive until sensors detect slip |
| AWD-type system with a low range | Yes | Yes | Jeep Active Drive Low (Compass Trailhawk) |
How Part-Time and Full-Time 4WD Work
A part-time 4WD system runs in two-wheel drive by default. Jeep explains that it has no center differential: in 4WD it locks the front and rear driveshafts together so both turn at the same speed. That gives strong traction off-road, but on a dry road the front and rear axles travel different distances in every turn. Because they're locked together, the tires have to scrub. Jeep calls the result crow hop: a bang, a shudder and tire scuffing, which can lead to early part failure. Ford's owner's manuals say the same thing: don't use 4H or 4L on dry, hard-surfaced roads.
Full-time 4WD adds a clutch or a center differential so front and rear can turn at different speeds. It can stay in four-wheel drive on any surface. Jeep's full-time Selec-Trac case, for example, has a 4WD Auto mode as well as 4H and 4L.
How AWD Works
Subaru describes two kinds of AWD. Full-time systems send some power to both axles at all times and use sensors to vary the split. Part-time or on-demand systems drive only the front or rear axle until sensors detect slip, then bring in the other axle. Neither asks the driver to do anything. Jeep's Quadra-Trac I on the Grand Cherokee is an always-engaged system of this kind, paired with a brake lock differential. Jeep notes it has no low range.
What Low Range Adds, in Numbers
Low range is a reduction gear in the transfer case that multiplies torque and slows the wheels. The combined effect shows up as the crawl ratio: first gear × low range × axle ratio. The higher the number, the slower and more controlled the vehicle can creep at idle.
| Vehicle and system | Low range | Crawl ratio |
|---|---|---|
| Ford Bronco Sport (4x4 with power transfer unit and rear drive unit) | No two-speed transfer case | 18:1 |
| Jeep Compass Trailhawk (Active Drive Low) | Yes | 20:1 |
| Jeep Wrangler Sport, automatic, 3.45 axles (Command-Trac) | 2.72:1 | about 44:1 (calculated) |
| Jeep Wrangler Rubicon, automatic, 4.10 axles (Rock-Trac) | 4.0:1 | about 77:1 (calculated) |
| Jeep Wrangler, maximum as equipped | 4.0:1 | up to 100:1 (Jeep claim) |
The Bronco Sport carries a 4x4 badge, but Ford's spec sheet describes a power transfer unit feeding a rear drive unit, with no two-speed case. Its crawl ratio comes from the transmission and final drive alone. The Compass Trailhawk is a crossover too, but Jeep's Active Drive Low adds a low range. The badge on the tailgate tells you neither.
How to Tell What a Vehicle Actually Has
- Look for a low-range ratio or a crawl ratio in the manufacturer's specification sheet. A two-speed transfer case lists one, for example "Low Range Ratio 2.72:1."
- Check the transfer case type: part-time or full-time, and the operating modes (2WD High, 4WD Auto, 4WD High, Neutral, 4WD Low).
- Read the owner's manual's 4WD section. If it tells you not to use 4H on dry pavement, the system is part-time.
Which One a Given Vehicle Needs
For paved roads in rain and snow, AWD or full-time 4WD handles the job without driver input. Tires set the limit on snow and ice; Subaru recommends snow tires whichever system you have. Low range earns its place when you need slow, controlled movement: Jeep lists steep climbs, getting out of a tough spot, rock crawling and pulling a boat trailer out of the water. If a vehicle will regularly see that kind of use, confirm a low range and a crawl ratio on the spec sheet before buying. See 4 high vs 4 low for how the two ranges are used, and when to use 4WD once you have one.
Recommended gear
A first recovery kit for any 4WD
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Best for a complete strap, shackle and glove kit in one bag.
- Straps, shackles, gloves, damper and a recovery bag in one kit.
- Covers most vehicle-to-vehicle recoveries without buying parts separately.
Best for getting unstuck from sand, mud or snow without another vehicle.
- Nylon recovery boards that give spinning tires grip in sand, mud or snow.
- Double as a shovel to clear sand from in front of the tires.
Best for airing all four tires down to a set pressure at once.
- Automatic deflators preset between 6 and 30 PSI.
- Air all four tires down at once, then stop at the set pressure.
Best for airing back up before you hit pavement.
- Portable 12V compressor rated to 150 PSI.
- Sized for truck and SUV tires.
We research products from manufacturer specs and owner feedback; we don't test them ourselves. How we choose.
Sources
- Jeep — 4x4 FAQ & Glossary — Jeep's definitions of part-time 4WD, full-time 4WD and AWD; AWD lacks 4-low on some vehicles; crow hop; Quadra-Trac I has no low range; heavy-snow and low-range guidance.
- Jeep — 4x4 Systems — Command-Trac part-time 2.72:1, Selec-Trac full-time, Rock-Trac 4:1, Quadra-Trac I always engaged with brake lock differential, Active Drive Low with low range and 20:1 crawl ratio.
- Stellantis Media — 2026 Jeep Wrangler Specifications — Transfer case types, operating modes and low-range ratios; gear and axle ratios used to calculate the 44:1 and 77:1 crawl ratios.
- Stellantis Media — Press Kit: What's New for 2026: Jeep Wrangler — Jeep's claim of maximum crawl ratios up to 100:1.
- Ford — 2025 Bronco Sport Technical Specifications — Bronco Sport 4x4 layout with a power transfer unit and rear drive unit, and its 18:1 crawl ratio.
- Subaru — The Difference Between 4WD and AWD — Subaru's definitions of AWD vs 4WD, full-time vs part-time (on-demand) AWD, and its advice that both AWD and 4WD vehicles run snow tires.
- Ford Owner's Manual — Using Four-Wheel Drive (2017 Expedition) — Ford: do not use 4H or 4L on dry, hard-surfaced roads.