Due to high torque requirements and difficulty in removal of the
transmission case to converter housing bolts without stripping the
internal torx, the bolt head is being changed to the new Mortorq
design. This requires use of a special 3/8″ drive bit that fits the
propeller-shaped recessed design of the Mortorq bolt. Once the
production change is completed, the Mortorq bolt will be the only one
available from GMSPO for service part replacements.

Kent-Moore
Tools DT-49037-A Driver, Mortorq Spiral Fastener