black_box

Assuming you change nothing between gear ratios/etc and go from a 4l60e to a th400 with say a 3k stall, approx. how much mileage is lost?

JL ws-6

iTrader: (50)

Around town, probably very little. On the highway, it's gonna suffer, the around town nmileage and highway, will probably be the same.

black_box

It wont bother me much, Ive been daily driving a th350/3.73 truck with mechanical secondaries for the last 3 years. Im just hoping to see any improvement, if it hits 16mpg on the freeway its nothing new.
How bad would you say the freeway mileage drops? With the gearing Im switching to Id probably be cruising at about 2500 rpms. Im hoping to hit about 20ish.

JL ws-6

iTrader: (50)

Alot of that depends on the motor. I can see it doing 20 mpg on the highway if you keep it at a reasonable speed, how much it will drop I don't exactly know. The non lockup is the real killer.