Buy the wrench for the fasteners you touch every day, not for the biggest number on the box. An oversized gun adds weight and air draw you will feel by mid-shift; an undersized one hammers at a seized nut and gets nowhere. And whether you call it an air impact wrench or an impact gun — same tool — the right size comes down to three things: drive size, torque class, and the air line behind it.
The 10-second answer
| Drive | Daily work | Torque class | Start here |
|---|---|---|---|
| 1/2" | Cars and light trucks — lug nuts, brakes, suspension | 500–1,620 ft-lbs | 1/2" drive wrenches |
| 3/4" | Fleet, bus, agricultural, medium-duty truck | 2,000–2,400 ft-lbs | 3/4" drive wrenches |
| 1" | Semi tires, heavy equipment, mining, construction | 2,200–3,000 ft-lbs | 1" drive wrenches |
1/2" drive: the auto-shop workhorse
Passenger and light-truck lug nuts spec in the 80–140 ft-lbs range, and most brake and suspension hardware sits below that. A good 1/2" gun covers the large majority of bay work, which is why it is the size most techs reach for first. Within 1/2", pick by body style:
- Micro — the AW-80JL puts 500 ft-lbs in a 2.3 lbs tool. Mobile service calls, strut towers, anywhere you are working at arm's length.
- Stubby — the AW-90J (700 ft-lbs, 2.7 lbs) and the AW-100T (700 ft-lbs breakaway in a 4.2" body) fit engine bays and wheel wells where a full-size tool will not square up on the fastener.
- Full-power pistol — the AW-140P delivers 1,450 ft-lbs at 4.85 lbs, and the AW-141P pushes 1,620 ft-lbs with an extended anvil for reaching through wheels and suspension clutter.
3/4" drive: the fleet tweener
Between car bays and semi yards sits a band of work — box trucks, buses, agricultural equipment, light industrial bolting — where 1/2" guns run out of breakaway and 1" guns are more weight than the job needs. That is 3/4" territory. The AW-172P runs 2,000 ft-lbs at just 7.1 lbs; the AW-222P steps up to 2,400 ft-lbs for oversized lug nuts and seized industrial fasteners while staying under 10 lbs.
1" drive: semis and heavy equipment
Modern semi wheels run 33mm flange nuts installed around 450–500 ft-lbs — and after a winter of road grime, breaking them loose takes far more than the install spec. This is where 1" anvils and big hammer mechanisms earn their keep: the AW-280GL (2,200 ft-lbs), AW-342GL (2,730 ft-lbs), and AW-382GL (3,000 ft-lbs).
One choice matters more than most buyers expect: anvil length. GL models carry an 8" extended anvil that reaches through dual wheels and deep-dish rims to the inner fasteners. GS models use a short anvil — the AW-280GS and AW-342GS keep the center of gravity close to the grip, which means better one-hand control in tight clearance. Duals and drop-center wheels: GL. Equipment work and cramped frames: GS.
Match the air supply, or the numbers never happen
Every torque rating assumes the tool is fed properly. AIRBOSS impact wrenches are rated at 90 PSI; what separates them is air consumption — 10.6 CFM (0.3 m³/min) for the AW-100T, 14.1 CFM (0.4 m³/min) for the AW-172P, 17.7 CFM (0.5 m³/min) for the AW-222P. Undersized compressors, narrow hoses, and worn quick couplers starve the motor, and a starved gun can lose a third of its rated output. Check the CFM figure on each product page against what your compressor sustains — not its peak rating — and run the hose diameter the spec sheet calls for.
Quick picks by trade
- Tire and general auto bay — one full-power 1/2" (AW-140P) plus one stubby for tight spots.
- Mobile mechanic — AW-80JL micro for weight, plus the strongest 1/2" your portable air can feed.
- Fleet garage — AW-222P for daily medium-duty, with a 1" gun on the rack for semi wheels.
- Heavy industry — AW-382GL for maximum breakaway, GS variants where clearance is the constraint.
Browse the full lineup in the AW Series collection, or jump straight to your drive size: 1/2", 3/4", 1".