Not following why going from the 727 to a 4 speed made a difference on the highway. In both cases you are running at 1:1 in the trans, unless you are using 3rd in the 4 speed or something.
Gear noise maybe? If so, maybe your 4 speed is going bad or something?
Really puzzled. If anything, the 4 speed should have dropped your highway RPM's a bit due to no longer having slip from a torque converter.
Did you change to a shorter tire at the same time?
