New to the forum, but not to Squarebodies...

[Keith Seymore]

1. I know the gears came with the truck, since they are on the build sheet. I looked the truck up on the build option chart posted elsewhere on this forum, and it would appear that they must have been special ordered, as the charts say that gear ratio was only offered stock on the K30 one-tons. Since they were put on this truck by Chevy, does that mean that other rear-end components were likely beefed up as well, or could the 4:56 gears just be paired up with the standard 3/4 ton axles, etc.?!

So - according to the chart above 3.73 was base; 4.10 and 4.56 were regular available options. Not special (other than being selected from the available offerings) and not beefed up beyond normal K20.

K

 

[BigT]

Generic info packet from the GM Heritage Center for a '78 pickup:

www.gm.com/content/dam/company/no_search/heritage-archive-docs/vehicle-information-kits/chevrolet-trucks/1978-Chevrolet-Truck.pdf

K

Aha!! I was looking at the "California only" sheet. That explains my confusion. Clearly CA has been "different" for some decades.... The good news is that I should no trouble getting gears that will work!!

Wow! Ida kept the 73/74 grille style. Love those.
Someone must’ve put an older core support n stuff in it. As those grilles are not supposed to fit in 75 (I think ) and up trucks because they set deeper than the newer models.
New one bolt right in?

Regarding gears, even if it was special ordered I’m fairly certain the axle is identical. 14bolt full floater.
That said, 4.56 is almost un driveable unless you never get on I 82 and only take back roads at 55mph.
I have 4.10s with new 35s and that is prohibitive for freeway driving imo.
3000rpms at 70mph roughly is what I get, just not conducive for driving the open road. I’d strongly consider you think about 3.73s tops and possibly a little higher even if it’s going to be a go everywhere daily driver.

Someone removed the grille brackets in order to make the earlier grille fit, so I had to get a new set of those with the grille. I like the early one, too, but the previous owner kept it, so I needed a new grille regardless.

I am considering 3:73s. The 1/2 ton I grew up with had those, and it was a good all-around ratio, though it had a manual transmission. I don't usually drive long distances much, so 4:10s may be sufficient, but we'll see. I'm too damn broke to do that right now anyway, so 4:56s will have to do for a while.

Welcome from the Motor City.

At your leisure could you please post up a pic of the build sheet?

K

Yes I will post that when I can get a minute to scan it. It's no longer attached to the glove box door, but it's in good shape.