My 08 Sierra with the 5.3 and 4l65e average 17 towing my little S & S from Clarksville TN to Mobile AL fully loaded down with the bed and cab full. Most have had a tail wind on the down hill drive. In 08 the 6l60 was available for the 5.3 too just didnt like the way it slid between gears and the thought of rebuilding a 6 speed over the venerable 4l60 variant
19' Skier 351W PowerSlot Deluxe
Long gone is the Trans AM
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