I know this gets asked a lot, but every combo is different right. It's hard to guess what I'll need so I am relying on all of your experiences. I just put a 12 bolt in my "70" Chevelle. Right now it is open with 3.08 gears. I want it to be quick off the line, but still be ok on the highway. I do mostly in town driving, and this is not my daily driver. It's just a serious street machine. I just want a happy medium gear set. I have been considering 3.42, 3.55, and 3.73 gear sets. I will be putting in an Eaton posi at the same time. Here's what I got...

468 ci (approx 10:1 comp)
781 heads (worked over)
Forged bottom end
Comp 270EX cam
RPM air gap
Edelbrock 750
Flamethrower HEI
Hooker headers
TH 350 W/shift kit
2400 stall
28" tall tires

I desk top dyno'ed my engine at about 500HP, 540 ft/lb. So what do you guys think? Any input would be appreciated. Thanks.

I as well as others here really like the 3.31 gears for all around driving & performance.

I don't think they make the 3.31 gears anymore. Do you think there is that much difference between the 3.31 and the 3.42 gears?

I second the 3:31s too,they are a good compramise for perf vs street cruising capbility when not running an auto OD trans like a 2004r /700r4 or a man trans with OD.

If you want 3:31's my friend and i both bought used sets off ebay and had them installed in our 12bolts with no problems from the gears after running them for 2 seasons. They cost approx $140-$150 per set used and you see them on ebay from time to time. I have even seen a coiuple NEW NOS sets of 3:31's from GM sell for approx $350.

But my yoke/pinion leaked like heck after the shop replaced the pinipon seal 2x.

I then decided to look at it,the lube was leaking through the spline inbetween the rear yoke & pinion splines which is very common. I then pulled the yoke off and there was no sealer at all on it at all so i cleaned everything with solvent,sealed it with silicone sealer,re-installed yoke, and trq to approx 100-125 ft lbs(used loctight on pinion nut),and let dry overnight.

I have driven it this summer approx 300-400 miles with no leaks at all,i cant believe the shop would mis that 2x in a row,sloppy work if you ask me for sure.

Scott

Ok, If I can't find any 3.31. Do you think 3.42 will be to low?

3.73's and a 2004R :)

The 3.42 is a very popular gear for limited highway use and good performance around town. There are no new 3.31s being made now, so you are limited to use gears there.