Rear Axles, What Changed in 1977 ?

[bucket]

The phasing out of the Dana 44 started during the '77 model year, for sure. It evidently took quite a while to use up remaining inventory of the completed Dana axles.

 

[Jawzjeep]

I can really only see that if a rear locker was installed.

People always say that the rear axle was narrower than the front to get the correct Ackerman angle. But the same rear axle width was used on short beds, long beds and K5's too, which blows that theory out of the water. My belief is that it was just to save money. The rear axle width is the same as the 2wd's which have a narrower front track than the 4x4's. It was just GM's way of getting more out of a single axle housing.

The other theory out there is that the rear axle won't follow the same ruts as the front axle. Imho, that's bogus because it's not a big enough difference to matter.

Sorry I've been out for a while..
I meant in all the squares the front is a wider track width. You can see it when your riding behind em. They look like they crabwalk a little since your looking down the drivers side.

And I understand and agree that gm used a bunch of the same parts for many rigs.

Ive got 3 sets of axles here that all would agree with me. Same rims front to back, no spacers. 91 4x4 burb, 78 4x4 k5, 84 4x4 k20. All the fronts track width is wider. I can take pics of your want? Not being smart either. The right info is the right info. I won't claim I'm right about it being for turning radius, that's just what I've grown to understand. The measuring tape doesn't lie though.

 

[bucket]

Sorry I've been out for a while..
I meant in all the squares the front is a wider track width. You can see it when your riding behind em. They look like they crabwalk a little since your looking down the drivers side.

And I understand and agree that gm used a bunch of the same parts for many rigs.

Ive got 3 sets of axles here that all would agree with me. Same rims front to back, no spacers. 91 4x4 burb, 78 4x4 k5, 84 4x4 k20. All the fronts track width is wider. I can take pics of your want? Not being smart either. The right info is the right info. I won't claim I'm right about it being for turning radius, that's just what I've grown to understand. The measuring tape doesn't lie though.

No no, I agree that the rear axles are narrower. There's no doubt about that at all.

It's just that a lot of people say that it was done that way for a functional purpose. There's the "different rut" theory and the "Ackerman angle" theory. I don't buy into either theory, I believe it was just GM being cheap.

 

[Jawzjeep]

No no, I agree that the rear axles are narrower. There's no doubt about that at all.

It's just that a lot of people say that it was done that way for a functional purpose. There's the "different rut" theory and the "Ackerman angle" theory. I don't buy into either theory, I believe it was just GM being cheap.

Ah ok, sorry i misunderstood.

 

[chris87]

My 79 k5 has the 10 bolt front and the 12 bolt rear. I'll putting adapter style spacers on my k5 in a few weeks. I bought steel ones and they are really well made.

https://www.motorsport-tech.com/partsgallery.html

I'll post pics as soon as they are installed.

I think the narrow rear axle was just to save money. 1 axle fits 53 truck

My 79 k5 has the 10 bolt front and the 12 bolt rear. I'll putting adapter style spacers on my k5 in a few weeks. I bought steel ones and they are really well made.

https://www.motorsport-tech.com/partsgallery.html

I'll post pics as soon as they are installed.

I think the narrow rear axle was just to save money. 1 axle fits 53 truck types sounds very GM to me.

Did you ever put these spacers on? I'm looking at the aluminum ones in 1.5 inches. I have an R10, long bed.

 

[ali_c20]

@chris87

Yes They are on, forgot to post the pictures. Everything works as it's supposed to. I had to retorque the spacers 2 times which is a bit annoying putting tires on and off the k5 for a few times.

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[rpcraft]

In 1978 they started replacing the 12 bolt rear and the dana 44 front with 10 bolts and it took a year or two for all the old stock to be phased out so you could have gotten a combination of one or the other, but I think they either did 10 bolts up front almost 100% and then a mix of 10 or 12 in back. If you are just ordering wheel spacers it should be fine regardless of what axle so long as it is the 6 lug half ton variant if everything is stock as you have mentioned. As far as spacers go the track width on the 10 and 12 bolt was the same on the rear axle, leaving about a 3 inch narrower difference between than the front axle so you could get a 1/12 inch spacer for each rear wheel if that is what you are trying to resolve.