willie Posted October 31, 2009 Share Posted October 31, 2009 can anyone help me figure out the #s on this rear, he dozent know much about it. These are the only #s on it that we can find GM55 3959038NF 1234587880 Thanks for the help in advance. Willie Quote Link to comment Share on other sites More sharing options...
monzaz Posted November 2, 2009 Share Posted November 2, 2009 3959038NF is the casting number of the rear. Is a 1969 carsting for chevelle and elcamino...could be a early 1970 monte...But since there was a GM strike in 1970 most montes got the pontiac tempest 10 bolt 8.2 in the early first 1/2 build year. GM55 ??? 1234567890 are nothing more that check digits to compare other number cast into the housing. If you look in the webbing around the rear cover you will find the actual casting date of the rear housing IE - L 12 9 meaning L= 12 month december 12 = 12th day of the 12 month 9 = 1969 year on the axle tube passenger front tube between the spring perch and cast center section pig will be stamped in suffix code 2-3 letter and more 4 digit number and another letter code ...plus there maybe a second row under that it might have a E or nothing at all. Quote Link to comment Share on other sites More sharing options...
willie Posted November 2, 2009 Author Share Posted November 2, 2009 he finally found the right set of #s its a CF code Thats one of ours Right? He said its from a 71 monte. Thanks Willie Quote Link to comment Share on other sites More sharing options...
monzaz Posted November 10, 2009 Share Posted November 10, 2009 CF on the axle tube passenger side would be 3.31 posi rear differential in chevelle monte or el camino 1971 or 1972 and could be 1970 also but in 70 they usually used 3 letter code CCF. Jim Quote Link to comment Share on other sites More sharing options...
willie Posted December 3, 2009 Author Share Posted December 3, 2009 I just got the rear its stamped CF0310B. What does the B mean,Where it was built? Jim you said the CF means it is a posi? I cant seam to find a second row at all, not even the letter E by itself. Doesnt it have to have that letter E to prove its a posi? Thanks for everyones help Willie Quote Link to comment Share on other sites More sharing options...
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