Latest Lost Cause Project: 1979 Z28

[Midnightmoon]

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[Midnightmoon]

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[Midnightmoon]

Side question for you. I took some pics of the rear axle today while I had it in the air. 31 spline 8.5 10-bolt correct? I didn't pull the cover, but by rotating the driveshaft, it appears to be somewhere around a 3.42 ratio which would make sense for an automatic equipped car I suppose.

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[bucket]

It should be 28 spline axles.

 

[Midnightmoon]

It should be 28 spline axles.

What does the 31 mean on the side of the housing? That's what has me asking the question.

 

[bucket]

What does the 31 mean on the side of the housing? That's what has me asking the question.

Damned if I know. It's nothing pertinent to the innards of the differential though. I'd assume it only meant something to a foundry worker.

 

[Midnightmoon]

Damned if I know. It's nothing pertinent to the innards of the differential though. I'd assume it only meant something to a foundry worker.

I appreciate the amount of accidental learning that happens during a project like this.

 

[77Dmax]

3.42s would be like winning the lotto. In addition to leaving the factory with no horsepower most of those cars got 2.56s, 2.73s and the occasional 3.08s. It was a very dark time...

 

[bucket]

3.42s would be like winning the lotto. In addition to leaving the factory with no horsepower most of those cars got 2.56s, 2.73s and the occasional 3.08s. It was a very dark time...

I thought I was lucky with my 3.08 and limited slip. It doesn't matter much though, it's still going to get a 3.90, lol.

Iirc, Z28's all got a 3.73 as standard.

 

[brooksman9]

Should be a stamping on the other side that you could decode I believe

 

[bucket]

The stampings are normally on the forward facing side of the passenger axle tube. They can be a real bear to read if there's any amount of rust. Be careful cleaning it off to read it, as too much cleaning can make the stamping even less defined. A wire brush by hand is the safest way that I've found.

 

[77Dmax]

I thought I was lucky with my 3.08 and limited slip. It doesn't matter much though, it's still going to get a 3.90, lol.

Iirc, Z28's all got a 3.73 as standard.

A quick Google search confirms your are mostly correct. Manual z28s got 3.73s and autos got 3.42s standard. I am shocked GM had that much of a pulse back then!

 

[Midnightmoon]

Found G 117 in that area

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[legopnuematic]

3.73s in a manual- that would explain why my dad said his neighbor growing up’s 79 Z-28 4 speed felt really quick.

Although, my grandparents at the time had a 1978 Caprice classic, 305 2 barrel and a 1980 Toyota SR5 pickup, so it might not have taken much for something to feel like a rocket.

 

[brooksman9]

From this post I believe there are some other numbers before that

Rear axle decode

Can anyone decipher this? I'm researching what I have and wonder if this is a z28 only rear end

nastyz28.com

Another good one

can someone tell me what rear end i have

i bought a 74 camaro and the orig owner said he put a nova rear end in it but it measures 45 1/2 center to center between spring perches and doesent look like they have been moved the axel tube is stamped pac 6232 1 only the bottom half of the numbers are stamped so i could be wrong on the...

nastyz28.com