Rear end identification.

Ocalanewport

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Looks like I need a new speedometer gear, my speedometer is off 5- 10 mph. I have a '65 Newport. Convertible 383 2bbl. Any ideas what rear end it has? Figured I'd ask the experts. Thanks!
 

detmatt

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8 3/4”.
What ratio? None of us would be able to tell you that for sure.
The best way to tell for sure is to safely Jack up the rear and see how many revolutions the driveshaft spins for every 1 full rotation of the tire.
 

marko

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what size tires are on it ? if the 14"s have been swapped for 15"s that could be the issue
 

68 4spd Fury

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I assume automatic trans? Standard off the line would be 2.76:1 unless it was ordered special. However, in 50+ years you never know what was swapped out. As stated, check tire size, jack up and count the rotations. Might also be a tag on the diff, if it survived, that has it on there.
 

tallhair

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Might as well provide brand and tire dimensions in full ie 235/70/15 etc while you’re at it and verify rear end type, most likely 8 3/4 but take a look to verify.
 

300L

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rearspotter[1].jpg


Pretty sure 8 3/4
A little help to verify your axle
 
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Is the speed off by a fixed offset like 40 and 70 are both off by 5 or is it at 20 it is off by 4 and 60 is off by 12 (IE 20%)?
If it is a proportion, just do the math. if it is 10% across the board, change the drive gear the same proportion, more teeth makes the speedometer read slower. If a 30 tooth is in the car now, and the speedometer is off by 10% fast, put a 33 tooth in.
If the spedo is off by the same offset, the needle is incorrect and easily adjusted, just move the needle to make it read correct.
My $.02
 

Ocalanewport

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Is the speed off by a fixed offset like 40 and 70 are both off by 5 or is it at 20 it is off by 4 and 60 is off by 12 (IE 20%)?
If it is a proportion, just do the math. if it is 10% across the board, change the drive gear the same proportion, more teeth makes the speedometer read slower. If a 30 tooth is in the car now, and the speedometer is off by 10% fast, put a 33 tooth in.
If the spedo is off by the same offset, the needle is incorrect and easily adjusted, just move the needle to make it read correct.
My $.02
Is the speed off by a fixed offset like 40 and 70 are both off by 5 or is it at 20 it is off by 4 and 60 is off by 12 (IE 20%)?
If it is a proportion, just do the math. if it is 10% across the board, change the drive gear the same proportion, more teeth makes the speedometer read slower. If a 30 tooth is in the car now, and the speedometer is off by 10% fast, put a 33 tooth in.
If the spedo is off by the same offset, the needle is incorrect and easily adjusted, just move the needle to make it read correct.
My $.02
Ok, thanks for the advice.
 
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