gotfords Posted November 29, 2020 Share Posted November 29, 2020 ok so i understand the tag means 2.75 with locker...also know the 9 mans 9" what i want to know is what the "S315A" means supposedly oem rear end in 80 f100 with 300 and manual trans but 5x5.5 bolt pattern??? oh and it says locker but when i jacked up rear off the ground I rotated one tire and the other side rotated the opposite?? did not think that was a sign of a locker??? thought if it was a locker both wheels would spin in same direction? or should i have spun drive shaft???? make a difference??? thanks Link to comment Share on other sites More sharing options...
Rembrant Posted November 29, 2020 Share Posted November 29, 2020 what i want to know is what the "S315A" means Assembly plant code I think. I don't think it's a useful number for your purposes. Somebody can correct me if I'm wrong. Link to comment Share on other sites More sharing options...
gotfords Posted November 29, 2020 Author Share Posted November 29, 2020 what i want to know is what the "S315A" means Assembly plant code I think. I don't think it's a useful number for your purposes. Somebody can correct me if I'm wrong. hoping to find exact production date Link to comment Share on other sites More sharing options...
Rembrant Posted November 29, 2020 Share Posted November 29, 2020 hoping to find exact production date That would be the 9L21. The 9 indicates 1979, the L indicates December, and the 21 is the 21st day of the month. What is the build date on your 1980? Link to comment Share on other sites More sharing options...
gotfords Posted November 29, 2020 Author Share Posted November 29, 2020 hoping to find exact production date That would be the 9L21. The 9 indicates 1979, the L indicates December, and the 21 is the 21st day of the month. What is the build date on your 1980? it says dec. 1979....close enough i guess...my marti report says built dec. 12th 5 days late actually they say...close enough i guess Link to comment Share on other sites More sharing options...
gotfords Posted November 29, 2020 Author Share Posted November 29, 2020 hoping to find exact production date That would be the 9L21. The 9 indicates 1979, the L indicates December, and the 21 is the 21st day of the month. What is the build date on your 1980? thanks for the help...kinda weird a 2.75 came with a locker...lol Link to comment Share on other sites More sharing options...
gotfords Posted November 30, 2020 Author Share Posted November 30, 2020 thanks for the help...kinda weird a 2.75 came with a locker...lol also kinda odd they would have been working on dec 21st tooo...it was a friday.....ususally they shut down for Christmas and for inventory for most of the month... Link to comment Share on other sites More sharing options...
myrl883 Posted November 30, 2020 Share Posted November 30, 2020 also kinda odd they would have been working on dec 21st tooo...it was a friday.....ususally they shut down for Christmas and for inventory for most of the month... S315A is the part number for the differential assembly, S indicates it was built at the Sterling axle plant. 9L21 is NOVEMBER 21, 1979... Link to comment Share on other sites More sharing options...
gotfords Posted November 30, 2020 Author Share Posted November 30, 2020 S315A is the part number for the differential assembly, S indicates it was built at the Sterling axle plant. 9L21 is NOVEMBER 21, 1979... thanks...i see how "L" is Nov. now...makes better sense for my build date of 12/12 Link to comment Share on other sites More sharing options...
Rembrant Posted November 30, 2020 Share Posted November 30, 2020 thanks...i see how "L" is Nov. now...makes better sense for my build date of 12/12 That certainly makes more sense. I did see somewhere before the M=December, but how do the months correlate with the letters?...since I got it wrong. Link to comment Share on other sites More sharing options...
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