sentences:  A Super Transtar featured a Detroit Diesel 12V71 V12 engine, allowing for loads of up to 144,000 lbs.The all-wheel drive Unistar was introduced; the truck was fitted with a freewheeling front axle, powered when the drive system detected loss of traction from the rear wheels; the Unistar was sold through 1972.During 1974, the Transtar cabover underwent a second upgrade, becoming the Transtar II (CO/COF-4070B).