ok so i have an 81 camaro 350 smallblock th350 tranny built with shift kit and the nthe 308 rear end. the other day a 5.0 mustang pulled along the side of me and started to pull away at 40 mph. even though i wasnt at full throttle i gave it gas and my mother was with me so i was in no position to keep goin. this pissed me off i have been wanting to get new gears and posi and was wondering what would be the best and also how much is 3:73 gears or 3:42 gears gonna bring done my gas mileage. as it is i get 10 mpg so i dont wanna take it down much furhter but next time i want some more pick up. thanks

 

Go down to the post titled "Picking right gears for rear". I gave a formula showing how to figure final rpmusing different gear ratios and tire diameters. Your 10 mpg, is that a lead-foot estimate, city driving,highway miles, or combo? How much highway driving do you do? That's where the difference in gas mileage is going to be noticed. If you never, or rarelyhit the highway, then go with alowerratio. During around town low speed driving, I would be surprised if yourmpg changes at all,it could even change for the better. With lower gears, your engine doesn't have to work as hard to get the car moving from a stop, think granny gear in a 4wd truck. Play with the numbers and do a comparison with what you have now.

 

Don't forget to mention the fact that what you give to the lower end you take from the top end. I've been there and I've done that. I finally went back to a 3.08 and now my Z is fun to drive, on and off the freeway.

 

3.73 posi.