Thread Repair Kit 348-Piece Metric and SAE Helicoil Set

Stripped threads are the part of a transmission job nobody plans for. Pan bolt holes in a cast-aluminum case pull out when somebody ran them down with an impact. Bellhousing and crossmember bolts gall and take the threads with them. Cooler line fittings, shift cable brackets, extension housing bolts, starter and inspection cover holes - all of them thread into soft metal, and once the hole is gone you either replace the case or you put a wire insert in it. This 348-piece kit is the second option, in a case, with every size covered.

The set runs the five metric sizes and five SAE sizes that cover almost everything on a driveline: M5, M6, M8, M10, M12 and 1/4 in., 5/16 in., 3/8 in., 7/16 in., 1/2 in. Each size gets a matched 135-degree split-point HSS drill bit, an oversize tap cut for the insert, a stack of coiled wire inserts, an installation mandrel and a tang break-off punch. Drill bits are high-speed steel; the taps and install tools are heat-treated alloy steel. HORUSDY part number 86591.

Bench procedure is the same every time. Drill the damaged hole out with the bit that matches the size you are repairing, tap it with the oversize tap that came with that size, run the tap in with cutting oil and back it off every half turn to clear chips, then thread the coiled insert in on the mandrel until the top coil sits about a quarter to a half turn below the surface. Snap the drive tang off with the break-off punch and blow the hole clean. The finished hole takes the original bolt at the original torque - you are not stepping up a bolt size or drilling for a bigger fastener.

Two things worth knowing before you start on a case: chase the chips out completely, because aluminum shavings that fall into a pan rail or a valve body bore will end up in the fluid, and if you are repairing a blind hole check your drill depth first so you do not break through into a passage. Everything stores in a molded case that keeps the drills, taps and inserts sorted by size, which matters when you are mid-job with the pan off. Kit weighs 7.4 lb; case is 14.57 x 11.57 x 2.8 inches.