Best Tcase/tranny combo for mileage?

[1976gmc20]

Originally Posted by OutlawDrifter

a well tuned carb, good plugs/wires/distributor, and a light foot can do wonders. my old k10 could do 15mpg if i drove it nice. it was a similar setup to yours.(350/350/203, 3.42 gears)

My 1980 K-10 (350/465/205) would get 18 mpg easy on the highway if you didn't drive too fast, and 15mpg at 80mph!

I don't know what the axle ratios were, but it was tall! You had to run up to about 35mph before shifting into high gear, so it was like a four speed overdrive. With the granny low it was still fine off road.