Rear Axle Ratio

J

js66coupe

Member

May 10, 2009

49

0

7

Florida

May 26, 2010

#1

• May 26, 2010

• #1

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

D.Hearne

New Member

Sep 29, 2000

11,730

6

0

south louisiana

May 26, 2010

#2

• May 26, 2010

• #2

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

Member

Mar 8, 2007

283

0

17

Minnasnowta

May 26, 2010

#3

• May 26, 2010

• #3

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

Active Member

Nov 29, 1999

1,551

1

37

May 27, 2010

#4

• May 27, 2010

• #4

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

 

6

65coupe408w

Member

Mar 26, 2010

192

0

16

May 27, 2010

#5

• May 27, 2010

• #5

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

Founding Member

Apr 12, 2002

6,698

550

204

tucson,az

May 27, 2010

#6

• May 27, 2010

• #6

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.