Any easy way to tell gear ratio - Chevy Nova Forum
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Old 16th-June-2017, 11:09 AM   #1
Winch
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Any easy way to tell gear ratio

I got a line on a complete rear end that came out of a 63. He thinks it was 6 cyl stick. It's a good hour away so I'm asking is there an easy way to tell ratio? I'll put it in my 62 which is an automatic and I think has 3.08 gears. What would a 6 stick have come with standard in 63?
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Old 16th-June-2017, 11:17 AM   #2
Corycarlo

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Spin the wheel once and count the drive shaft revolutions I believe....
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Old 16th-June-2017, 11:23 AM   #3
Winch
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Yeah, I know how to do that but the seller says "maybe I can do that" but I'm not sure I want to drive that far based on what he determines. I'd like to know if I want it before I do. I am hoping all 6 sticks were a standard ratio. I need to research that a bit more.
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Old 16th-June-2017, 12:06 PM   #4
Winch
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Wow, I'm way off thinking my automatic has 3.08 gears. I just checked it and it takes a little over 1 1/2 turns of the pinion yoke to turn the wheel one full revolution. That tells me it's more like a 1.56 rear right? I didn't know they came that high.

I just found this : http://www.novaresource.org/axle.htm

In the chart for 1962 and 1963 it shows all cars except wagons came with 3.08 regardless of engine size. I guess that 63 will be OK.

Last edited by Winch; 16th-June-2017 at 12:12 PM.
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Old 16th-June-2017, 12:14 PM   #5
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Both automatic and manual transmissions had 3.08 gears in a coupe or sedan rear from 63.
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Old 16th-June-2017, 12:16 PM   #6
Winch
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Quote:
Originally Posted by dlove63 View Post
Both automatic and manual transmissions had 3.08 gears in a coupe or sedan rear from 63.
I didn't mention my 62 is a convertible. Still 3.08?

Does that mean you need to spin the wheel 2 full revolutions and count the revolutions of the yoke?
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Old 16th-June-2017, 12:37 PM   #7
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Quote:
Originally Posted by Winch View Post
Wow, I'm way off thinking my automatic has 3.08 gears. I just checked it and it takes a little over 1 1/2 turns of the pinion yoke to turn the wheel one full revolution. That tells me it's more like a 1.56 rear right? I didn't know they came that high.

I just found this : http://www.novaresource.org/axle.htm

In the chart for 1962 and 1963 it shows all cars except wagons came with 3.08 regardless of engine size. I guess that 63 will be OK.
You need to understand the science of differentials. If you rotate the input shaft until you have 720 of rotation of the output shafts, you will have the ratio. If the output shafts are tied together, as in a limited slip differential, each wheel will rotate its 360, resulting in 720 of total rotation. If one output shaft is held stationary, you must continue to rotate the input shaft until the other shaft has rotated 720, or two full turns. Given your results you could estimate that the ratio is near 3.08.
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Old 16th-June-2017, 12:37 PM   #8
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lets see how did that guy tell me at the car show last sunday. how many turns of the drive shaft to turn the tire one revolution. so mine is a 3.55 posi so i guess 3 1/2 turns of my drive shaft turns my tire once. think thats how he said it was.
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Old 16th-June-2017, 01:16 PM   #9
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lets see how did that guy tell me at the car show last sunday. how many turns of the drive shaft to turn the tire one revolution. so mine is a 3.55 posi so i guess 3 1/2 turns of my drive shaft turns my tire once. think thats how he said it was.
Tires. Plural. If 3-1/2 turns of your driveshaft turns one tire one revolution, you have a 7.00 rear gear ratio. If 3-1/2 turns of the driveshaft turns both tires one revolution, you have a 3.50 ratio.
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Old 16th-June-2017, 01:56 PM   #10
Winch
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Originally Posted by Mike Goble View Post
You need to understand the science of differentials. If you rotate the input shaft until you have 720 of rotation of the output shafts, you will have the ratio. If the output shafts are tied together, as in a limited slip differential, each wheel will rotate its 360, resulting in 720 of total rotation. If one output shaft is held stationary, you must continue to rotate the input shaft until the other shaft has rotated 720, or two full turns. Given your results you could estimate that the ratio is near 3.08.
OK that makes sense. The only time I remember checking one like this was when I had a 4.11 posi in a 67 Vette.
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Old 16th-June-2017, 03:03 PM   #11
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In '63, the ratios were 3.08 or 3.36.

If there's still an ID stamp legible on the axle (passenger side tube, forward side of axle), you can see what was installed from the factory. There's no guarantee that that's what's still in there, but it's a start.
The first two letters are the ratio code. The rest is build information (date, plant, and posi type).

Axle codes for '63 (from NovaResource):
DA - 3.36 open
DB - 3.08 open
DC - 3.55 open (4cyl - 3 speed manual)
DD - 3.55 posi (4cyl)
DE - 3.36 posi
DF - 3.08 posi
DH - 3.08 posi (6 cyl)
DJ - 3.08 open (metallic brakes)
DK - 3.08 posi (metallic brakes)
DL - 3.36 open (metallic brakes)
DM - 3.36 posi (metallic brakes)
DN - 3.55 open (4cyl - metallic brakes)
DP - 3.55 posi (4cyl - metallic brakes)


The only reliable ways to tell what's inside the differential, without a legible stamp, are to spin and count (as discussed), or pull the cover and start counting teeth.
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Old 18th-June-2017, 02:02 PM   #12
Winch
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Let me ask this: is there any difference in 62 vs 63 rear ends? I'm thinking of buying this 63 rear end and just swapping the differential and axles. That way I don't have to undo the brakes or remove the housing etc.
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Old 18th-June-2017, 06:37 PM   #13
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If only it were as easy as pulling the cover...none on a '62-'63, it's a dropout pumpkin. Counting the wheel and driveshaft revs as has been carefully outlined works, and it's very probably 3.08's.

'62 brake hardware is old style, with a star wheel on the brake shoe spreader for manually adjusted brakes. '63 is the first year for self-adjusters. Backing plates are the same, just the brake hardware is different. Axles, housing, bearings, seals...all the same '62-'63, I believe. Hard to get parts for anymore, especially wheel bearings (just saw a new set sold here on SNS by a member) and rear brake drums.
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Old 18th-June-2017, 06:42 PM   #14
Winch
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You might remember I have already converted the brake hardware on my 62 to include the self adjusters. As long as axles and differential are the same it should be an easy swap. I'll have the luxury of being able to disassemble the 63 with it not under the car so I'll get a little experience pulling those parts.

I do remember looking for axle bearings a while ago. I hope either of mine are still good.

Last edited by Winch; 18th-June-2017 at 10:48 PM.
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Old 19th-June-2017, 09:42 AM   #15
Winch
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Another question: Once the pumpkin is out, how hard is it to replace the bearings in it? Does it require disassembly of ring and pinion and thus setting those up correctly again?
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