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Can anybody help me in identifying this C2 diff please. Said to be a 1967, 3.73 ratio.Is there a way to identify from these photos whether its posi or not please, I am not currently where the diff is located.
AO is the code for a 65 to 67 3:70 Positraction differential, that one is dated 2 3 67. It's possible the inner gears may have been changed, but a quick turn of the driveshaft yoke and counting the revolutions of the half shaft yokes would confirm or otherwise establish the ratio now in the case . . . .
Turn half shaft yokes 1 complete revolution and count the revolutions of the driveshaft yoke. That will give you the gear ratio. Use a black or white or yellow marker to mark each yoke for counting.
If you rotate the driveshaft yoke and BOTH half shaft yokes turn in the same direction, then you have a POSI rear. If not, then you have an "open" rear (non-posi).
Turn half shaft yokes 1 complete revolution and count the revolutions of the driveshaft yoke. That will give you the gear ratio. Use a black or white or yellow marker to mark each yoke for counting.
If you rotate the driveshaft yoke and BOTH half shaft yokes turn in the same direction, then you have a POSI rear. If not, then you have an "open" rear (non-posi).
Larry
Since you're not able to turn the half shaft yokes yourself, you'll be dependent upon the other party to perform the checks outlined above. I'd think you'd be able to trust someone to do this for you . . . . . you be the judge . . . . .
Turn half shaft yokes 1 complete revolution and count the revolutions of the driveshaft yoke. That will give you the gear ratio. Use a black or white or yellow marker to mark each yoke for counting.
Larry
I would add, for clarification, rotate the half shaft yokes one full rotation. If the driveshaft rotates 3.7 times in order for the half shaft yoke to rotate once, it has 3:70-1 gears.
Last edited by A-Snake; Jan 3, 2022 at 01:46 PM.
Reason: error
I would add, for clarification, rotate the half shaft yokes until the driveshaft makes one full rotation. If the half shaft yoke rotates 3.7 times in order for the driveshaft to rotate once, it has 3:70-1 gears.
huh? think about it…..
Last edited by 66427-450; Jan 3, 2022 at 12:49 PM.
AO is the code for a 65 to 67 3:70 Positraction differential, that one is dated 2 3 67. It's possible the inner gears may have been changed, but a quick turn of the driveshaft yoke and counting the revolutions of the half shaft yokes would confirm or otherwise establish the ratio now in the case . . . .
Thank you for sharing your knowledge Ron, much appreciated
If you can't pull the rear cover for an in depth look you are only guessing. It's one thing to know the ratio but it's more important to know the condition. If the posi is cracked it will break with a 370 or any ratio. If the diff was rebuilt, it's only as good as the guy who worked on it. Date code is important for a correct car buy you may be rebuilding it just like I had to do last week with a previous rebuilt diff. The housing was one year, the posi completely different and cracked. It was sold that way!
C2 Diff Identification Help Please
