gear ratio for 67 Coronet
 

I need more performance than my 2.94 gear ration is providing. 1967 Coronet, 383 with 727 3 speed automatic. Suggestions of how big before being too big? 3.55 or can I go higher?

You can go as high as you want, I have 4.88s in my Volare but you will not find me anywhere near the interstate with it. If your 383 is stock or a mild build a 3.23 or 3.55 are good street gears, if gas mileage isn’t a concern and your cruising is 55 miles an hour or so 3.55 or 3.73 gears are a blast.
So 3.55 is a good compromise gear, and probably what I go with unless you are planning a 500hp build for your 383…cash

I like the 3.91 gear set.... Good for the large heavy cars...

I had a set of 4.10s in a 77 royal Monaco at over 5000 pounds it ran low 15s with the smog 440…!

Cal -

What RPM will you be comfortable with on the highway?
I ran 3.23's for decades on a 2 ton+ Charger with a modified 440.
Worked well, but recently switched to 3.91's - runs better, @ highway speeds, 3000 is about average, but remember it's a built 440.
3.23 will show a mild improvement, 3.55, 3.73 are mid range and 3.91 is about as high as I'd go with a non-race car.

Archer

Back in the sixties the 3.91 set was a popular OEM performance option.

I do like most all the 4.XX raito's, But like all have said, Those you have to ready to use a bit more RPM when driving out on the Highway or Interstate..
And the Fuel mileage goes away pretty quickly.... But if you got on of them big old honker camshafts that start the rpm range at around 3000 rpm and that about were the converter in locked in.... Then you can run a 4.30 - 4.88 gear and do ok...
It just take some planning ad some adjustments that always leads to more fun money....
Keep us posted..... :)

Cheers

i have found, in almost all apps, that 3.55 is a great universal ratio. not mild, not wild, just right. :D