Short answer: on a lifted truck, buy for maximum lift height and chassis length. Capacity is a distraction — a jack lifts one corner, and one corner of a half-ton pickup is well inside 3 ton. What goes wrong is that the jack tops out with the tire still on the ground, or the chassis is too short to reach a frame rail from the side of the vehicle.
Measure this before you shop
Park on level ground, find the frame rail or axle you intend to lift from, and measure floor-to-lift-point. Then add the amount you need the tire to come off the ground — 2 to 3 in is enough for a wheel-off job, more if you are pulling a brake drum. That total is the minimum maximum-lift figure your jack must publish. On a 4 in lift with 35 in tires, a great many owners find the number lands between 20 and 24 in, which is exactly the band where most 3-ton jacks stop.
Published maximum lift, ranked
| Jack | Max lift | Min height | Format |
|---|---|---|---|
| Sunex 66035HR | 24.4 in | 3.58 in | Steel high-reach jack |
| Powerbuilt 620471 Unijack | 21 in | 11 in | Bottle jack with locking bar |
| BIG RED T83006 | 20-7/8 in | 5-7/8 in | Steel trolley jack |
| Sunex 66035SJ | 21.2 in | 3.85 in | Steel service jack |
Why chassis length matters as much as the ram
On a car you lift from the sill, a few inches in from the edge of the vehicle. On a truck the strong points are frame rails and axle tubes, which sit well inboard of the rocker panel and behind a much wider tire. A short jack physically cannot get the saddle there. The Sunex 66035HR has an 18 in extended chassis and the Arcan A20016 a 32 in one; that reach is the difference between reaching the rail and lifting from whatever you can touch, which is how bent pinch welds and dented fuel tank straps happen.
The thing ramps cannot do here
Ramps are a genuinely good tool on a truck for oil changes — see car ramps for trucks — but they support the vehicle on its wheels. Anything that takes a wheel off needs a jack and stands, and on a lifted truck that means checking the reach of both. The capacity guide works through why the tonnage number is not the constraint.