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64 Diff. Code?

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Old 11-12-2011, 09:58 PM
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K5kaos
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Default 64 Diff. Code?



Wondering if anyone can help make out this code on 64 vert. diff?
Old 11-12-2011, 10:00 PM
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K5kaos
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Here is an overall view.
Old 11-13-2011, 04:07 PM
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JohnZ
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The Julian date code (3 3 4) pretty much confirms that it's a '78 or '79 3.55 Posi ("OH") axle, made on the 334th day of the year. The casting date will be on the driver's side, partially hidden by the front of the strut rod bracket.
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Old 11-13-2011, 11:23 PM
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K5kaos
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Wow, John!!
Thanks!!
Your knowledge base is amazing!
Here is another pic from the same diff.
Located on rear pass. side
Old 11-13-2011, 11:27 PM
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More pics:


Old 11-14-2011, 12:29 PM
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JohnZ
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Yup - the 464910 rear cover was used in '78-'79, with the 7/16" rear spring retainer plate bolts (vs. the 1/2" bolts used from '63-'77) to accommodate the '78-up 2-1/4"-wide spring.
Old 11-14-2011, 12:52 PM
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MiguelsC2
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St. Jude Donor '10-'12-'13

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Welcome to the Forum! Your in the right place.

Old 11-15-2011, 02:45 AM
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K5kaos
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Thanks 1sttexan!
I agree.
I've always enjoyed the wealth of info on this site!
Old 11-15-2011, 02:52 AM
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JohnZ,

As you stated in an earlier post, there is a P-code on the side of the muncie 4-speed in my car.
It is: P8T18
If I understand it correctly that means it was built on December 18th,
1967 , for a 1968 car.

Still not sure if it is a M20, M21 or M22.
Old 11-15-2011, 11:18 AM
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Originally Posted by K5kaos
JohnZ,

As you stated in an earlier post, there is a P-code on the side of the muncie 4-speed in my car.
It is: P8T18
If I understand it correctly that means it was built on December 18th,
1967 , for a 1968 car.

Still not sure if it is a M20, M21 or M22.
That's correct. Pulling the side cover and looking at the helix angle of the gears is the sure-fire way to tell, but it's highly unlikely that it's an M22. If the rpm drop from 3-4 is the same as it is from 1-2 and 2-3, it's an M21; if the rpm drop from 3-4 is much greater than it is from 1-2 and 2-3, it's an M20.

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