Does anyone know what the "SPEC" cast into a 9 in carrier means does it have anything to do with nodular?
As far as I know, nodular differentials are identified by the "N" casting in the carrier and the machined area for the brinnell test. I've never seen one with "SPEC". Do you know what it was in originally?
Yes it is in a 67 GT500 . I saw someone advertising a 67 in the last snake bite and they also listed it had the SPEC carrier so I checked mine and it said the same thing .I thought some Nodulars did not have the N ?
I'm not sure if it was any different from the standard C7 E case used in most 9" apps. It certainly doesn't look different. The N cases used the 31 spline axles so in a Mustang app they would only be in CJ's and Bosses. Tim
Tim mine had the 31 spline ,Spec case, and a 3.25 to 1 open rear end still with the tag in place . Was it only C.J s and bosses or Big block and bosses that had 31 spline?
Well I certainly can't say all or none. My 68 500 has its original rear and its a 28 spline. I can say I've seen a lot of 28 spline big blocks. My 67 GT 500 had its original drivetrain but I never had chuck/axles out. Heck I don't even remember seeing spec on the case but who was looking back then. I asked around to some knowledgable automotive proctologists and though the consensus that spec stands for special, no one really knows what is special about it. Rumor has it they were also used in Nascar cars.
I just got some pictures and more data. The spec case clearly has the extra vertical ribbing like the N case so it is different from the C7 case used with 68 500's. I also see a C4AW B casting on the inside which is the early version of the N case. It was originally used in 427 Galaxie applications. Some of the early ones had the N on the case. It is a high nodular (magnesium added) casting and used the 31 spline axles like Magstar has indicated. Most likely the spec or special casting was to indicate it was for Shelby applications as the standard 67 S coded cars received the C7 case though I can't confirm this. See what a little research can do? Tim
Yes Tim mine also has the casting on the inside C4AW-B and the extra rib on the front and a bigger inner front pinion bearing. Thanks for the info.
