1/2 in High-Torque Cordless Impact Wrench Kit, 700 ft-lb

Every transmission job starts with bolts that have been sitting under a vehicle for a decade. Crossmember bolts, driveshaft flange bolts, bellhousing bolts, torque converter nuts, axle nuts, exhaust hangers in the way of the pan. This is a 1/2-inch brushless cordless impact wrench that hits 700 ft-lbs of tightening torque and 1000 ft-lbs of breakaway torque, which is enough to crack loose anything you will meet under a car without dragging an air hose across the shop floor.

It runs the CRAFTSMAN V20 battery platform and ships as a complete kit: tool, a 4.0Ah lithium-ion battery, and the charger. Model number is CMCF940M1. The brushless motor is what buys you the runtime - you can pull a crossmember and a driveshaft on one charge instead of swapping packs halfway through. Three speed settings plus a variable-speed trigger let you back off for smaller fasteners so you are not shearing off a 10mm pan bolt with a gun built for axle nuts.

On the bench and under the car the practical details matter more than the torque number. There is an LED on the nose, which is the difference between finding the last bellhousing bolt and feeling around for it. At 12.2 inches long it clears the tunnel on most trucks and still gets alongside a bellhousing where a full-size air gun will not fit. The whole kit weighs about 10.1 lbs in the box. Use a torque wrench for final spec on anything that calls for one - an impact is for removal and for running fasteners down, not for setting torque on a converter or a valve body.