Quote:
Originally Posted by custom10nut
A few questions here.they come from seeing a SPID for a 72 K-10, (4spd equipped) on a FB truck page.
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So - having said that - we really need a bit more detail about your truck.
I'm going to assume it's a '72 K-10, based on your question (but if not the analysis will be the same):
Quote:
Originally Posted by custom10nut
The SPID listed a POSI Traction Rear differential.
How common are the and/or are they hard to find?
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They were certainly available originally; finding them now might be problematic.
Quote:
Originally Posted by custom10nut
Whatever Gear would have been in this Rearend? ( I’m assuming it would be 4.10)
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No way to know.
Looking at the base content chart in the Info packet I linked (page 6) shows the standard axle as 3.73.
Checking the powertrain charts (page 10) shows an optional 3.07 ratio in addition to the standard 3.73, confirming what Richard and Casper posted earlier.
So that's not too bad (50/50 odds) but you can't know because you don't know what the original owner chose. Plus open vs posi, so that takes you to one in four odds. Better than I thought it would be, and better than usual.
Quote:
Originally Posted by custom10nut
If I were to find one, would it be possible to change the 4.10 to a more Highway sensible ratio (3.55 or lower )?
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Yes.
Quote:
Originally Posted by custom10nut
Last question would be: what would the Factory Part numbers be?
(So that I know that I’m getting an Actual POSI unit)
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That's a big "ask".
Rear axle assemblies proliferate based on series, C vs K (sometimes), locking vs open, rear axle ratio, brake series or friction material (sometimes).
So somewhere there is, or was, a chart of 20 or 30 permuations that laid out the various part numbers - and the corresponding code stamp on the axle tube.
Any commodity that proliferates like that (rear axle, transmission, engine, shock absorbers, springs, radiators, etc) has a chart like that, or did at one time.
You are going to be hard pressed to find that list of part numbers, after 50 or 60 years, and even if you did there's no guarantee that ratio or carrier is still what's inside the axle.
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