dallasite21

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?

joe_padavano

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.

joesw31

A set of 3.36s or 3.55s should work.

gearheads78

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