Depth Micrometer Set 0-6 in for Clutch Pack Clearance

A 0-6 inch depth micrometer with a 4 inch hardened base, six interchangeable measuring rods and 0.001 inch graduations, packed in a fitted case. The rods thread into the same spindle and the barrel does not need to be re-zeroed when you swap from the 0-1 inch rod up to the 5-6 inch rod, so you can chase one measurement across several depths without stopping to reset the tool. Accusize part number 2025-4201.

The reason this belongs on a transmission bench is clutch pack clearance. Once the pack is stacked and the snap ring is seated, you bridge the drum with the 4 inch base, run a rod down onto the top pressure plate, and read the distance to the snap ring or the drum face. Compare that to the factory spec for the unit -- most GM and Ford packs land somewhere between .030 and .080 inch depending on plate count -- and you know immediately whether to change the selective plate or apply plate rather than finding out on the dyno. The same measurement taken at three points around the drum tells you if the plate is sitting cocked.

It does the rest of the depth work too: pump gear pocket depth against gear thickness when you are checking pump side clearance, case bore and servo bore depth, the distance from a case face down to a thrust surface when you are picking a selective washer for end play, and stack height on a valve body when a spacer plate has been swapped. Anywhere you would otherwise be guessing with the tail of a caliper across an uneven surface, the flat base gives you a real reference plane.

Read it like any micrometer: bring the rod down with the ratchet stop, not your fingers, and let it click through twice before you take the number. Wipe the base and the part face first -- a chip of clutch material under a 4 inch base will cost you a couple thousandths, which is exactly the range you are trying to resolve. Rods, base and case are included; no setting standards are needed for the 0-1 inch rod since the base face is the zero reference.