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Discussion Starter #1
hi ,
I just purchased a Mustang and have a few questions in regards to decoding a Vin number with a vehicle this old. I am trying to find out what rear end gears belong in that vehicle for that specific vehicle? I want to make sure no modifications were made by if they were I know what they were I don’t want to take the cover off to verify if I don’t have to but the Ford dealer told me they can’t decode my vin does anybody know how to decode a vin from his year?
 

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Discussion Starter #2
i am having a speedometer issue and am not sure if the previous owners have changed out the gears. the speedometer jumps around u til u get up to 50 or so ,
when it says i’m going 60 i am going 78 so trying to see if it may just be the speedo gear or if there are different gears in the rear end. so i have a couple things i’m trying to find out with out puttin on a lift to do
 

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Your VIN doesn't normally list your axle ratio. Per my '95 shop manual, the modern VINs break down as:

1,2,3 - Ford
4 - Restraint Type
5 - Ford Passenger Vehicle (versus Lincoln, Mercury, other, or non-US cars)
6,7 - Body Style
8 - Engine
9 - Check Digit
10 - Model Year
11 - Assembly Plant
12-17 Production Sequence Number

If your car still has the original Certification Label on the door that might tell you the axle code that you could look up.

The jumping might mean that the cable is kinked somewhere, or it might need to be lubed. Where it goes into the back of the gauge might need to be lubed too.

Your tire size may also be throwing off your speedo. If the tires are a lot bigger than what came on the car originally that will make the speedo read slower.

Hope that helps. I don't know a lot about the 80s models but maybe that can get you started.
 

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Dimples
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Shouldn’t there be a tag on the rear end? Not that it couldn’t be swapped and still have the tag but it’s a start. Also verify that you have the stock size tires.

But based on the description, it doesn’t soumd like your speedo cable is very happy.
 

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Discussion Starter #7
Blake,
no tag on rear cover anymore. i will have to look at the speedo cable and see if i find anything. tires are correct for year
 
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