[manuellivingston]

Originally Posted by GOAT8U2

Need some help here...

1969 GTO, auto, 400, had many nice and somewhat uncommon options.

This rear end, 8.2, N = Nodular.
The rest of the numbers I don't know really.

Many years ago, I did a rear gear calculation by spinning wheel and counting mark on DS and came up with 3.55. But this might be incorrect and I noticed...

Mark on right axle housing literally says 3.08 L.
Above that is T-468.
None of the other GTO rear ends I've seen show the actual gear ratio on them. I can't find the HX or HY etc mark on the driver side but I thought it was there at one point. quenq vice city

Rear end is gone

Based on the markings you've described, the "3.08 L" stamp on the axle tube is a strong indication that the rear axle originally had a 3.08:1 limited-slip (Safe-T-Track) differential. Pontiac and GM axle assemblies were often marked with the gear ratio and differential type during production, so that stamp is generally more reliable than a wheel-rotation estimate performed decades later.
The "N" on the center section identifies the nodular iron carrier, which was a desirable heavy-duty component and commonly found on performance-oriented applications. The "T-468" marking is likely a casting or production code, but by itself it doesn't directly identify the gear ratio.
As for the missing axle code (HX, HY, etc.), it's not uncommon for those stamps to become difficult to read after years of corrosion, repainting, or cleaning. If the housing is no longer available, the axle tube stamp may be the best surviving evidence of the original gearing.
Given the information provided, I'd lean toward the rear end being an original 3.08 Safe-T-Track unit unless you have documentation such as the build sheet, Protect-O-Plate, or factory invoice indicating otherwise. The previous 3.55 estimate could easily have been affected by counting error, especially with a limited-slip differential and the vehicle not being fully unloaded during the test.