Even though we were told that the transfer case would be fine bolted to the back of the 4L80, we opted for the additional transfer-case mount from STAK to assure that the 150-pound three-speed doesn't break the tailhousing off the tranny. The mount comes with a slotted half-moon bracket and a bushing with tabs. We mounted the tabs as close to the Daystar tranny mount as possible to keep the drivetrain mounting points in somewhat of a triangle. We then welded a short tube to the bushing to hold the back of the case in place. This also reduced the shifter vibration in-cab as a bonus.