Good Afternoon. I would like to get some advice about the right gear ratio to use on my big block cutlass. I am going to have my rear end rebuilt and want to select wisely. My current set up is a fairly stock 455 with TH400 tranny and a 12 bolt chevy rear end. Currently has open rear end with 3.73 gears. I have 20'' wheels on the back with 275/40/20 tires so im about 29'' in total diameter. With that being said I plan to put in a posi rear end but I am struggling with the gear ratio. I dont like the way my 3.73's rife on the highway, but I still want to be able to burn some rubber in the city if so desired. What are your opinions of the 3.31 vs. the 3.55 gears for my setup?

 

Keep the 3.73s, swap the TH400 for a built 200-4R. The 2.74:1 first improves off the line response, the 0.68:1 fourth knocks those 3.73s down to a mileage-friendly 2.53:1 final drive ratio on the freeway.

 

A set of 3.36s or 3.55s should work.

 

Like I said in the text 3.31 if no plans for an overdrive. 3.73 if you think OD is in your future.