Hey everybody.
I'm going to be putting an Eaton posi in the bird and would like to get some opinions as to what rear gear I should go to.

Car Stats (305 LO3 w/ 700R4 trans):
Trick Flow® Super 23® 175 Cylinder Heads
Edelbrock Performer TBI intake manifold
Full MSD Ignition w/6AL box
Jet Stage 1 chip

The car currently has a 2.73 and I'm trying to keep it expressway friendly so I'm leaning towards a 3.23. What do you guys think? Will I notice a difference in performance? Would a 3.42 be all that bad? The car currently spins at about 1750 rpm at 70mph so what should I expect with a 3.23? Thanks for your input!

 

If my math is right I would expect about 2070 RPM at 70 with the 3.23 gears and about 2200 RPM with 3.42 gears with no other changes. Overall not a big difference between 3.23 and 3.42 tgears. Hope this helps.

 

id go 3.42 for some highway fun. i wouldnt be scared to run 3.73 with the overdrive tranny, but thats just me. sure would make that 305 feel more snappy.

 

expressway, is that just a short time? I know when ever Iam out on the highway, dam if Iam not wishing for that 2.77 gear back

Driving around town with the auto, no big diff bewtween them gears. Unless you jump on it. 2.77 to 3.27 was 500rpm diff on the highway, also took 50 mpg outta the tank for soild highway drives.

No long drives on the highway, I would go with 3.42's

 

I have 3.73s with my T-10 (no overdrive) it screams on the highway, but holy s*** fun around the back roads and from stoplights!! With overdrive I would say 3.42 wouldn't be a problem at all even with a fair amount of highway driving. I would even think about 3.73 but thats just my $.02

 

I have 3.42 and that's a good gear for street/strip

 

Wow, 500 rpm difference? Seems like a lot. The car is now actually pretty peppy with the new cylinder heads. Those plus the performer tbi manifold really woke the car up. I'm surprised by how much one wheel scratch it gets from a stop and now. In the old days it would just move forward when I stomped on it. Coming out of a turn sucks now too with an open rear, always roasts the one if my foot is too heavy haha. Maybe I'll just get a new carrier and keep the 2.73's? I know it's a 305 but I feel the last things I want to do to it are the holley throttle body, hooker 255 headers and mandrel 3" exhaust and a custom prom chip. The jet chip is now pretty dicy until the car kicks into closed loop. I think now it can do way better than 16.95 in the 1/4 haha

So if I go to a 3.23 what gear would I need for the trans to make my speedometer correct?

And thanks for all of the replies!