When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Pictures show better than what I looked at before. I don't believe that is a 69 differential. They would have the date stamped on it not in Julian dating. The casting date code is on the lower left corner of the housing, a letter and 2-3 numbers ie; A249= Jan 24 1969 OR 1979. Seeing that it appears to be painted, could just be my old eyes, I would say it is most likely a replacement and later C3. That actually isn't such a bad thing. No, the correct coding for a 69 is wrong but the later diff's had better posi cases and spiders than any 69 diff. They both had weak axles, case hardened. The later C3 had weak clutches and issues with ring gear bolts. The 69 had a much weaker posi case and spiders, but used solid steel clutches.
Bottom line, there was not one year that didn't have some issue. Some more than others. If that diff was replaced, maybe, it was correctly built and better than stock.Based on decades of working on these cars, seeing how people worked on them, I would be surprised if it was more than a common stock diff.
Pictures show better than what I looked at before. I don't believe that is a 69 differential. They would have the date stamped on it not in Julian dating. The casting date code is on the lower left corner of the housing, a letter and 2-3 numbers ie; A249= Jan 24 1969 OR 1979. Seeing that it appears to be painted, could just be my old eyes, I would say it is most likely a replacement and later C3. That actually isn't such a bad thing. No, the correct coding for a 69 is wrong but the later diff's had better posi cases and spiders than any 69 diff. They both had weak axles, case hardened. The later C3 had weak clutches and issues with ring gear bolts. The 69 had a much weaker posi case and spiders, but used solid steel clutches.
Bottom line, there was not one year that didn't have some issue. Some more than others. If that diff was replaced, maybe, it was correctly built and better than stock.Based on decades of working on these cars, seeing how people worked on them, I would be surprised if it was more than a common stock diff.
Looks like the casting date tells the story ... the casting date shows this is a 1978 C3 differential! Thanks all for your input to help decipher this - special thanks to Gary R for describing the differences in the 69 rear and the various later rears!
Your bottom picture shows the casting date but it also shows an axle seal leak and the cast lip for the seal appears to be impacted by the axle. This is common in C3 diff more than C2's. The original axles were good to about 50k miles, give or take. I would check to see how much endplay is in the axles. Driving it like this will leak to possible damage to the housing and the cost to machine sleeve it would be more than just replacing it. The lip should be about 1/8" at the seal.
C3 Differential year
