Neiko 01407A Electronic Digital Caliper, 6 Inch / 150 mm (Inch, Fraction, Metric)

Half of getting a transmission rebuild right comes down to measuring things, and a caliper is the tool you reach for over and over. Checking the thickness of a worn thrust washer against a new one. Measuring a clutch steel or a selective snap ring before you order the next size. Setting clutch pack clearance. Confirming the depth of a bore or the length of a fastener before it goes back in. Do it by feel and you find out at final assembly, or worse, on the test drive.

This Neiko caliper covers 0 to 6 inches (0 to 150 mm) with a resolution of 0.0005 inch and stated accuracy of 0.001 inch, which is plenty for the tolerances you deal with on a bench. The quick-change button flips the large LCD between decimal inch, fraction, and millimeter, so you can read a spec sheet in one unit and a parts catalog in another without stopping to convert. Two sets of jaws plus the depth probe let you take outside, inside, depth, and step measurements with the same tool.

The body is polished stainless steel with a knurled thumb roller and a locking screw that holds the reading while you pull it out to look. It is splash and dust resistant, which matters around a bench that always has a film of fluid on it, and it comes in a hard case so it survives living in a toolbox drawer. This is the caliper a lot of shops keep on the bench simply because it is accurate enough, easy to read, and cheap enough to not baby.