Rear Axle Ratio

[js66coupe]

I've got a 66 coupe under restoration. Planning a 408W w/ a C6 transmission. Rear has been upgraded to a 9 inch housing. However, I still need the center section. I have a used one which needs a rebuild. What ratio should I go with given that I'll have a 408W, C6, and 17" wheels. Planning for a street, part strip cam. Looking for a reasonable RPM on the highway.

 

[D.Hearne]

3.50's to 3.70's. Wheel diameter has little to do with it. It's the diameter of the tires you're running that affects the final drive ratio. My 77 Comet cruises nicely at 70 mph turning 3 grand with a C=4, 3.50's and 295/50/15's ( 26.5" tall)

 

[65FBE2]

I would go with 3.25's on a auto and 3.50's with a man trans. The extra slipage in a auto will net about the same hwy rpm. Anything lower will make the car faster but at a trade off. If drivability on the hwy is important don't go any lower.

 

[tx65coupe]

Since you don't have OD, I would stick with about 3.20 gears.

 

[65coupe408w]

I am running a 408w with a 9inch but have a GForce T5...I am running 3.70's in the rear and turn about 2000rpm at 75. The OD on my 5spd is .59 though I am running 245/45/17 in the rear. I wouldn't go with anything over 3.70's if you are concerned about highway rpm...

 

[rbohm]

what i would do is run a 3.00 gear for normal day to day driving, and swap to a 3.70-4.11 gear for the track. swapping pumpkins on a 9" rear shouldnt take you more than about 15 minutes when you get the hang of the swap.