Since cordless impact drivers have a complicated mechanism to burst their torque which fires often, build quality is more important than in regular cordless drills. To select a drill with excellent build quality you want to go with manufacturers that have proven their build quality over the years, and you want to check that users have successfully used the drill over the long haul.
And then you also want to make sure you get the right size cordless impact driver. One of the most demanding applications would be removing lug nuts from vehicle wheels. One of the most common applications is driving screws into concrete or less difficult materials. There's a large difference in torque required for these two applications.
If you want to know more about impact drivers and how they differ from cordless drills read on below the recommendations.
Makita has two "versions" of 18V impact driver. We're recommending the Makita BTD142HW 18-Volt Compact Lithium-Ion Cordless Impact Driver Kit,
but there's also and LXT model with about 800 more in. lbs. of torque.
But it's also over $100 more than this model. Here's why we selected this model:
It's no secret that we like Milwaukee's V28 system. It earned our recommendation for best 24V cordless drill. The Milwaukee 0779-22 V28 28-Volt Lithium Ion 1/2-Inch Cordless Impact Wrench is the impact driver in the V28 system. The torque is impressive at 3,900 in. lbs.
The real question is whether this drill can handle the sort of tasks that you would buy this type of drill for. Namely, can it remove and install lug nuts on wheels and other high-torque tasks. There were a few reviewers who said it wouldn't do these tasks for them. Basically, there were 3 guys that said it wouldn't and 10 that said it would. Normally that would make me nervous, even though there's good reason to doubt those three reviewers. Sometimes you hand tighten a lug nut to 150 (or whatever) and it takes way more torque to get it off. That's just the way lug nuts are.
But ordering a Milwaukee from Amazon also can alleviate your fears. They're both good about standing behind what they do.
If you're not happy there's a good chance they'll make it right.
So if you have to money to plop down on this sort of tool and you want a cordless tool for high-torque tasks, this is the way I'd go.
Research the Makita V28 Impact Driver at Amazon
A cordless drill provides constant torque. That means it "twists" with exactly the same force as long as you're holding the trigger down. But a cordless impact driver uses a spring to store some of its energy and then deliver that engery in small bursts. But don't think of an impact driver as jerky, like someone pumping the brakes on a car. An impact driver will deliver these bursts thousands of times a second. So to a human the drill feels almost smooth constant torque.
But the result is very different. By storing energy and deliver it in bursts an impact driver is able to deliver 3 times or even much more maximum torque (that is, torque during the burst) than a comparable cordless drill. This is great for driving screws or tightening/loosening difficult nuts/bolts. This is because a nut will tighten to the maximum torque you apply to it. And to loosen a nut you need to "break" it just once and then it's much easier to turn. Screws, likewise, don't require constant force either. The material you're driving into will not be 100% uniform. There will be small catches when more force is required to move the screw forward. That's why impact drivers excel at driving screws into concrete.