[RamAir]

Newbie to the forum and I just acquired a '72 LeMans Sport Vert, PHS documented 400, M22, 3.55 posi. It has the "N" code stamped on the diff. I am being told that this is a rare diff only installed in Judges and RamAir IV cars but Pontiac installed them in Vert's because of a flex issue. Any one know of this claim?

Thanks in advance

['ol Pinion head]

Welcome to PY board!

Nodular 8.2 housings were used by Pontiac in '67-72 Pontiac 8.2 10 bolt A-body applications where a 3.55 Safe-T-Track or 3.90 or 4.33 HD Safe-T-Track were specified. There are quite a few different casting numbers of these housings, some applications there are even two casting numbers for the model year. All will be Julian dated, so if one is a serious restorer, one will need to know the casting # needed, then one starts looking at the Julian date.

The 4.33 ratio had run its course by the time the 71 A-body models were introduced & only a very few '71 400 M22 A-bodys were built with 3.90 HD Safe-T-Track rears. For '71 & 72, that leaves the 3.55 Pontiac 8.2 10 bolt Safe-T-Track A-body rears to have the nodular housing. Quite a few of these were built. Know I've owned half a dozen just from these years & have copies of buildsheets & invoices from many more such equipped cars..

As far as Judges go, I've owned several '69 Judges that were auto a/c cars, they received gray iron 8.2 housings, not nodular housings. same deal in '70. All the '71 Judges came std with the 455HO & as such came with 12 bolt rears, not Pontiac 8.2 10 bolts. hope this helps answer your question.

[pont406]

OPH I have a Nodular 8.2 housing from a 67 GTO in my stash, my 66 lemans has the "gray iron" housing in it currently with Moser Axles, T/A Performance cover, 3:90 gears, Eaton Posi, car currently is street/strip car running high 12's, would it be a "no brainer" for me to swap my parts into the N housing as it wouldn't cost much at all to swap everything over, a set of springs and a seal/ bearing or two.

[RamAir]

So the "N" stipulates a Nodular differential?. I checked the numbers on the RF tube and it has the "XH" code, indicating a 3:55 Locking, yet the differential is painted gray. I'm confused, what's the difference between the Nodular casting and the gray? Is the Nodular more desirable?

['ol Pinion head]

yes the N casting stands for nodular iron, a better form of cast iron than the standard gray cast iron. Casting of the nodular iron 8.2 center housing was to minimize pinion deflection under high torque loads. the gray iron small pinion bearing design 8.2's allowed for a lot of deflection.

[RamAir]

Thank you very much for the information, much appreciated!