I recently came across an old post in a Chevy forum which claimed (albeit unconfirmed) that on occaision GM (Pontiac) changed rear Diff gears at a moment's notice on the assembly line once a particular vehicle was near shipping but which was suddenly identified for a partiuclar US region and then completed post-build sheet. The reasoning was that the Emissions Era gears could not adapt simultaneously to the needs of high mountanious terrain vs vast desert highways vs intermittent elevations in the various American markets and so ad-hoc changes were made during final assembly (?) without correction to the original build sheets or otherwise changed prior to shipment to the first originating dealerships.
Strangely enough, I discovered this opinion shortly before I began servicing my own rear Diff, and low-and-behold my gears don't currently line-up with the PHS documents I have. Long story short, the miserable 2.41 turns out to be a 2.56 (equally miserable, and certainly *NOT* an upgrade by anyone of any sound mind) with a PHC axle code for 1977 (I have a 1976) and not sure if this was a prototype-fix for its destination to South Carolina or what. Date coding the axle lines up with the original drivetrain assembly period along with all the other casted numbers identified throughout. PHS was contacted and they assume it to be an "unexplained"' thing that happened at the plant. So I'm back to Square One....
Yeah, I researched this as far my patience went and found no clues.
If anyone has any insights and expertise on this it would help settle my OCD-nish, LoL.
Strangely enough, I discovered this opinion shortly before I began servicing my own rear Diff, and low-and-behold my gears don't currently line-up with the PHS documents I have. Long story short, the miserable 2.41 turns out to be a 2.56 (equally miserable, and certainly *NOT* an upgrade by anyone of any sound mind) with a PHC axle code for 1977 (I have a 1976) and not sure if this was a prototype-fix for its destination to South Carolina or what. Date coding the axle lines up with the original drivetrain assembly period along with all the other casted numbers identified throughout. PHS was contacted and they assume it to be an "unexplained"' thing that happened at the plant. So I'm back to Square One....
Yeah, I researched this as far my patience went and found no clues.
If anyone has any insights and expertise on this it would help settle my OCD-nish, LoL.
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