How does the 6L80/90 compare to the 4L80 in parasitic drag? If I'm not mistaken the reason for the 6.0 Chevy trucks getting so much worse mileage than the 5.3's is largely due to the 4L80. Does the 6L80 have the same issue? The gear ratio's are fantastic on and the tap shift would be so useful off road. The 42RLE is a pile. In 4Lo it shifts from 1 to 2 and 2 to 1 at the worst times.