19CAMARO85

iTrader: (5)

I have an open diff. 3.23 Rear end. (Says RPO codes) I want to put a posi until in my car but i want to keep the factory mpg. My iroc is all stock and i plan to basically keep it that way. I was wondering however how much a 3.73 rear gearing would effect my gas mileage. I might know a guy with a set of them but i want to keep my MPG. thanks -Matt

JamesC

iTrader: (5)

3.23's are a great all-around gear, IMO. You would, no doubt, lose some mileage with 3.73's.

JamesC

19CAMARO85

iTrader: (5)

hey man, thanks alot I am still learning about drivetrain so its good to have some more experianced gear heads to learn from thanks man By the way you think that 3.42 would be pretty close to what im getting? This way it gives me a range to look from 3.23-3.42 thanks -Matt

JamesC

iTrader: (5)

Probably, but what makes a difference where gears are concerned is "how" you drive. With my 3.23's if I drive around town in second and third at 2500 or 3000, I may get 10 mpg.

JamesC

19CAMARO85

iTrader: (5)

yea, well since mines a auto i just kinda go with it lol Doesn't seem to bad other than at 55 mph its at 3000

WIll36

iTrader: (12)

If you switch to 3.73s you might actually get a little better milage around town cause the motor doesn't have to work as hard to accelerate the vehicle, but you will lose some of your highway milage. I like the 3.42s I have in my 88. Much better than the 2.73s I used to have since they forced my too cruise around town in 3rd instead of 4th gear. I would either stick with the 3.23s or go to a set of 3.42s if the car sees a lot of highway driving. Also 3000 seems rather high for 55mph with a 700 since my camaro is turning about that rpm at 75, 80. What size tires do you have on the car and are you sure your hitting 4th gear?

19CAMARO85

iTrader: (5)

ummm i believe its stock rear end... im not for sure, i have the factory size tires. The tranny i dont know when its been flushed out and a new filter installed but i havn't payed attention if im hitting fourth. My old 86 Z28 stayed at about 2500 at 55 so i dont know.

19CAMARO85

iTrader: (5)

Drove the car yesturday and i did shift through all 4 gears. It shifts from first at like 15-20 mph. But it does shift and doesn't seem to have anything wrong with it.