i have a 94 z that is pretty much stock except for cai,tb-bypass it has 323 in it now with 98,000 miles my question is i would like to put in 373 in it . how much fuel difference would there be ?? and how much would there be in hp and/or tq difference..open to all suggestions. thanks harry

 

I'm assuming that with 3.23s you have a 4L60E...Unless youre gonna spend most of your time at the track I would strongly consider 3.42s...The 4L60E has a 3.06 first gear which is huge...for comparison the old TH350 has a 2.52 first gear. Combined with 3.42s the 4L60E gives you a 10.465 first gear drive ratio....this is more out of hole grunt than a TH350 with 4.10s (10.332)...You'll still blow the tires off the wheels w/o some sort of Drag Radial (26" tall max or youll kill the ratio) and rear suspension work, lower control arms, etc, but you'll still get decent mileage...imho 3.73s are hard to control w/o a track tire like an ET street, etc...by the way, my LPE 383 with 420 rwhp gets 25 mpg on the highway...and in 9 years I've only rebuilt the rear once and that was due to my supposed Pro Auburn actually just being a regular Auburn...
--Alan

 

What are your goals or expectations by changing gears? If it's for 1/4 mile gains, I think most guys are going to suggest getting a stall converter (3000 - 3500) and leaving the 3.23's. I can tell you from my own experience changing from 2.73's to 3.73's that my fuel economy was actually about the same, except highway mileage suffered slightly, but I only noticed on long highway trips.

Also, changing gears doesn't really change the HP or TQ of the car, they just help apply it to the ground easier. I think some have actually seen lower HP on a dyno after installing lower gears.

IMO, the change from 3.23 to 3.73 is not really worth the effort.