The engine and transmission are out of a 1994 GMC Yukon. The TBI 350 V-8 was in great shape and needed no modifications. Jeff used the Yukon wiring harness as well, but removed many unnecessary wires. The GM 4L60E automatic had some upgrades, including a lock-up on-command torque converter. When placed in 1st or 2nd it won’t shift on its own; when you select 3rd (drive) or overdrive the transmission shifts like any normal automatic. Behind it sits an Atlas 4-speed transfer case with an 8.16 low-crawl ratio.