1987 c10 manual 4 spd.. factory trans?

[Tom]

Originally Posted by 1976gmc20

I get roughly half again the mileage out of a four speed manual versus the three speed automatic.

That's not normal. They have the same final drive ratio. By bypassing the compound low first gear your getting the same number of gears to accelerate threw. You should get about 10-15% better mileage, not 50%.

Something's wrong if you're only getting 10mpg in a pickup with a manual. Maybe you're running it up too high before shifting...? I can shift my C-20 out of 2nd (don't normally use 1st) at around 8mph, and get into 3rd by 20.

Apples to oranges. I had a medium to large size cam, RPM intake, holley 750DP, MSD iginition, headers with dual exhaust, 275/60/15 tires, 3.73's,385 stroker, vortec heads and 10:1 compression in the 78. Yes, the 79 with the vortec 350/200-4R got 15mpg on the freeway, but city mileage never changed. Besides all that, how is accelerating to final gear by 20mph at all fun?