Rear End Ratio

[Ed51]

My 63 Impala was originally a six with 3 on the tree. Over the years I ended up with a 427 and a Muncie 4 speed. In the last few years I've added EFI, rewired it,added Vintage Air ,etc. I have always been reluctant to really shift this thing hard. I think I would probably gack the rear end. I've finally decided to get a 9 inch to firm things up. What would the original six banger rear end ratio have been?

 

[BSL409]

most common if seen is 3.08 3.36

 

[Ed51]

I guess I'll split the difference and get a 3:25. There are no tags or ID that I can see on it.Thanks guys.

 

[BSL409]

on the other side of the punkin from the cast numbers will be another set of numbers post those

 

[Blk61409]

Jack up the rear end or put on a lift. Mark one rear tire, mark the driveshaft, put in neutral, rotate the tire one revolution and count how many times the driveshaft turns. If it turns almost exactly 3 times plus a little bit, 3.08, 3 times and about a 1/3rd a 3.36, 3.55, 3.70, 4.11, 4.56, 4.88 etc

 

[denson1932]

straight stick was 3.36 and auto was 3.08 and overdrive was 3.70. If you now have a close ratio 4 speed with 2.20 first gear then don't go below 3.50 rear end gears. If you have the wide ratio 4-speed with 2.54 first gear you can go with the 3.25 rear end gears.

 

[1964SuperStocker]

I don’t understand the use of the original question. It’s kind of irrelevant. No matter what is already in there you have to decide what is the best for your drive train combo. Tire size, trans, cam, torque converter or clutch. Even the kind of clutch/converter you run will make a difference. Not to mention how much highway use it will get or track time. Remember, you might like how the car performed before with the factory set up but if you match your rear gear properly then you will be very happpy regardless of what you had before.