ACDelco ARM601-4 1/2-Inch Digital Torque Wrench

This is ACDelco's ARM601-4, a 1/2-inch drive electronic torque wrench with a working range of 14.8 to 147.5 ft-lbs (20 to 200 Nm). The LCD reads live torque as you pull, and the tool beeps, flashes an LED and holds the peak value when you hit your target, so you are watching the fastener instead of listening for a click. It reads in ft-lbs and Nm, and it has a peak mode and a trace mode: peak holds the highest number reached, trace shows torque in real time as it builds.

On a transmission bench this is the wrench for the medium-torque work that a click wrench guesses at. Torque converter to flexplate bolts, bellhousing bolts, case-half and extension housing bolts, pump bolts, crossmember and mount hardware, and driveshaft straps all land inside 15 to 150 ft-lbs. GM 4L60E converter bolts run in the mid 40s ft-lbs, TH400 pump bolts in the upper teens to low 20s, and 4L80E extension housing bolts in the mid 30s -- all comfortably inside this wrench's accurate band. Note the low end: at 14.8 ft-lbs minimum this is not the tool for valve body or pan bolts, which are specified in inch-pounds. Keep an inch-pound wrench for those.

Accuracy is +/-2 percent clockwise and +/-3 percent counterclockwise from 20 to 100 percent of full scale, and it meets ASME B107.14.14-2004 and ISO 6789. Each wrench is individually serialized and ships with a matching certificate of calibration traceable to N.I.S.T., which matters if you are a shop that has to show a paper trail on torque-critical work. Body is composite with a soft grip and the head is metal; it runs on four AAA batteries (not included) and comes in a hard blow-molded case.

One habit worth keeping with any electronic wrench: pull smooth and slow through the last 20 percent of the target. Jerking the handle overshoots the reading before the buzzer catches up, and on aluminum transmission cases an overshoot is a stripped hole and a heli-coil.