Rear axle ratio from VIN - Chevelle Tech
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post #1 of 11 (permalink) Old Oct 4th, 12, 11:03 PM Thread Starter
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Greg
 
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Rear axle ratio from VIN

Does anyone know if its possible to find out my rear axle gear ratio from my chevelle's VIN number? I've been under the car too many times and theres just too much rust on the axle tubes to find anything. If it helps I have a 1970 chevelle 396/350 SS 4-speed. I'm pretty sure that its <3.31 because the previous owner said that the rpm's would let the car just "purr" at 60mph on the highway. Thanks.

-Greg
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post #2 of 11 (permalink) Old Oct 5th, 12, 12:00 AM
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Re: Rear axle ratio from VIN

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Originally Posted by Greg.H View Post
Does anyone know if its possible to find out my rear axle gear ratio from my chevelle's VIN number?

Bill Pritchard
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post #3 of 11 (permalink) Old Oct 5th, 12, 12:17 AM Thread Starter
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Greg
 
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Re: Rear axle ratio from VIN

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Originally Posted by Bill Pritchard View Post
Is there anywhere else that I can find it besides the rear axle assembly? I really dont want to try and crawl under there again just to come up with nothing.
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post #4 of 11 (permalink) Old Oct 5th, 12, 1:22 AM
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Re: Rear axle ratio from VIN

you could turn the axle and calculate the ratio. It seems that you want the original ratio though. Axle tube, build sheet, window sticker, protecto plate, sales paperwork.

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post #5 of 11 (permalink) Old Oct 5th, 12, 1:23 AM
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Bill
 
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Re: Rear axle ratio from VIN

You can get a ballpark number, by jacking the rear wheels off the ground, then turn the wheel one revolution, and count how many times the drive shaft turns. The best way is to pull the cover off and count the teeth on the ring and pinion gears. If it's that nasty under there, it's probably a good idea to pull the cover anyway, to change the gear oil.
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post #6 of 11 (permalink) Old Oct 5th, 12, 2:16 AM
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Re: Rear axle ratio from VIN

If it has the original gear, most in likely it is a 3.31 if you have a real L34 car. Jack the car up and use a scotch brite pad. You can find it.

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post #7 of 11 (permalink) Old Oct 5th, 12, 11:15 AM Thread Starter
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Greg
 
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Re: Rear axle ratio from VIN

Thanks guys, I think I'll try counting the turns of the driveshaft to one turn of the wheel, but I may also change the gear lube since the car is completely stock and it has most likely never been changed.
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post #8 of 11 (permalink) Old Oct 5th, 12, 11:42 AM
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Re: Rear axle ratio from VIN

You have a 42 year old car/rear.
Might be time to replace the gear lube so I'd drop the cover and get the numbers off the ring gear during the needed lube change.
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post #9 of 11 (permalink) Old Oct 5th, 12, 2:01 PM
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Re: Rear axle ratio from VIN

Quote:
Originally Posted by Greg.H View Post
Does anyone know if its possible to find out my rear axle gear ratio from my chevelle's VIN number? I've been under the car too many times and theres just too much rust on the axle tubes to find anything. If it helps I have a 1970 chevelle 396/350 SS 4-speed. I'm pretty sure that its <3.31 because the previous owner said that the rpm's would let the car just "purr" at 60mph on the highway. Thanks.

-Greg
I have the same setup (396/350 hp with 3.31 rear end) and at 60 mph on the freeway it is more of a "roar" than a purr. It's totally looking for a higher gear.

ACES #07817
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post #10 of 11 (permalink) Old Oct 27th, 12, 5:31 PM Thread Starter
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Greg
 
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Re: Rear axle ratio from VIN

I finally came home and had some time to check out the car. When I jacked up the car and turned the wheel one revolution, the driveshaft only turned 1 1/2 times around. I know that this isn't a very precise way to find the rear axle ratio, but there's no way it can only be 1.5:1. Does anyone know why this happened?

I also went under with some sandpaper and tried to find the code on the axle tube. I looked on the rear passenger side of the tube, is this the right place? Thanks for any help.
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post #11 of 11 (permalink) Old Oct 28th, 12, 11:23 AM
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Re: Rear axle ratio from VIN

Quote:
Originally Posted by Greg.H View Post
I finally came home and had some time to check out the car. When I jacked up the car and turned the wheel one revolution, the driveshaft only turned 1 1/2 times around. I know that this isn't a very precise way to find the rear axle ratio, but there's no way it can only be 1.5:1. Does anyone know why this happened?

I also went under with some sandpaper and tried to find the code on the axle tube. I looked on the rear passenger side of the tube, is this the right place? Thanks for any help.
Correct location is the front side of passenger side axle tube. GM says 8" inboard from the backing plate but that's a guide. As noted 3.31:1 would be typical for a 396/350 and should start with CCW then a 4 character date like 1025.
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