I have a B-body (96 Buick Roadmaster) but wanted to get some wisdom from this forum.

I have a LT1 with LT-4 corvette valve covers with full comp cam, 1.6 roller rockers, 915 bee hive valve springs with new seals, etc.

The tranny is 4L60E automatic.

The torque converter is 2400 stall, not sure if lock-up or not.

The rear gear is 3.73 and that's what my question is about. I get great performance at under 50mph but on the highway, the MPG is abysmal, about 18MPG and the RPMs are just too high for my taste, turning 2700 RPMs at 80MPH.

Question, could I get either 3.08 (The 96 Impala SS gears) or 3.23 without negatively affecting anything? I realize I will lose a bit of performance in the city and gain highway and gain MPG, at least 2-3MPG.

I was told my cam likes higher RPMs but what exactly does that mean? If I could get away with a numerically lower gear like 3.08 or 3.23 that would make me happy, as 3.73 is just not a great highway gear. Even 3.42 would be an improvement for me versus 3.73.

I had 3.23 gears once and liked them but that was with a stock L05 engine and stock stall (1400).

Basically I am trying to understand the relationship between cam, gears and stall speed. Can you use 2400 stall with 3.08 gears and a full comp cam?

 

This means that your cam performs best at high RPMs and may have some loss in the low end while still having a strong mid range. This is why bigger cams require you to shift at higher RPMs for best performance.

 

That would be an awful combination (big cam, tall rear gear), IMHO.

Rich

 

I've had 3.42 and now 3.73 and I have to say not much of a difference. Of course I have an f-body with a 3000 stall. Also, is it illegal to drive 80 MPH? LOL.