Hi Jason, and congrats on getting such a nice oletruck (I'm partial to
59 fleetsides)!
I don't know anything about the numbers, but I can usually tell what a
rearend came out of by looking at it. If it's a 3/4 ton, it will have
8 lug wheels. If it's an original 59 Chevy 1/2 ton rearend, it could
either be the non-posi type and have a removeable front section, and a
round removeable rear cover plate, both held on with 10 nuts, or it
could be a Dana 45 posi rearend, with a stop sign shaped rear cover held
on by 10 bolts. If it's a later truck rearend, it would probably have
12 bolts holding on the cover. The ratios of the original 1/2 ton rears
are almost always about 3.90, while the later rearends are usually 3.73
if they are 6 lug, or possibly 3.07 or 3.40 if it's from a newer 4x4.
You can check the ratio of a rearend by holding one wheel still, turning
the other wheel two revolutions (exactly), and counting the turns of the
pinion yoke (or driveshaft)...the number of turns is the ratio.
You mentioned wanting to go to five lug wheels, are you going to make
the front wheels five lug also? You can do this by going to disc
brakes, or by using 51-54 car front hubs.
The stock 4 speed, and any other non-overdrive tranny, will have a 1:1
high gear ratio. There aren't really any simple 5 speed overdrive
swaps, although you could visit a junkyard and look at late 80s-90s
vintage Chevy trucks and see what's invlolved. The 700R4 is a good
swap, if you get a good tranny, which may be expensive (or not,
depending on your luck). If you do go with an automatic, or any tranny
that does not have the bellhousing mount, you'll want to make sure the
engine is properly supported with side mounts, not the factory front
mounts.
The rearend from a Camaro or Nova (70s vintage) may be what you want; if
you don't get overdrive, then a 3.08 gear would probably be about
right...measure first to make sure it's the right width, and you'll have
to swap the spring perches, which involves welding and careful measuring
(the angle is important).
So many choices...
Jim
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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