Rear Axles, What Changed in 1977 ?

[440sixpack]

I was ready to order some 1 1/2' spacers for the rear axle of my '77 K10 and noticed the product says '77 up. I think my rear axle is original but the glove box sheet says I have posi and I don't so I'm not positive. what is different in 1977 so I can be sure before I order ?

 

[Octane]

As far as I know all 77 had the 12 bolt rear in it.As many others did.Mine does.And I have the front diff 10 bolt corporate as 77 was a transition year going from dana 44 to 10 bolt.The rears didnt change as far as I know.Not until subsequent year models anyway.

 

[440sixpack]

I have a 12 bolt rear and a Dana 44 front. the spacers are for the rear to correct the narrow axle thing so it shouldn't matter then. I think the rear went to a 10 bolt as well but not until the 80's I' thought.

 

[Jawzjeep]

Just saying and not trying to sway your opinion but having a rear narrower than the front will give you a better turning radius.

 

[bucket]

Just saying and not trying to sway your opinion but having a rear narrower than the front will give you a better turning radius.

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.

 

[RoryH19]

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.

I was just having this debate with someone. Heard the narrow track for better traction, possibly stability and turning radius. Common platform as 2wd makes the most sense to save money.

 

[RoryH19]

I have a 12 bolt rear and a Dana 44 front. the spacers are for the rear to correct the narrow axle thing so it shouldn't matter then. I think the rear went to a 10 bolt as well but not until the 80's I' thought.

My 78 k10 has a 12 bolt with limited slip and the front is a Dana 44.
I believe they started moving to corp 10 in the front this year and the rear in 81.

 

[bucket]

The 10 bolt front started showing up during the '77 model year. The rear started showing up in the early 80's.

 

[PrairieDrifter]

It's a game of the draw. My 79 has a Dana 44 front and a 12 bolt rear.

 

[440sixpack]

So if this is the case why would they draw a line at the '77 model year ? I may have to call them but I bet they can't give me an answer.

Normally I wouldn't mess with it I don't like modifications and I'm no fan of spacers and adapters. but it just looks crappy being so narrow, I just want to square things up.

 

[Bennyt]

If you don't like spacers, you can use an axle out of van. I know the 14B FF were the same width as front axles but don't know on the 1/2t models.

I had to trailer my K5 one or two times and the only way it fit was backed on trailer so in that rare instance, it came in handy. For reference, my K5 had D60 and 14b ff and 12.5 wide tires.

 

[ali_c20]

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.

 

[GMFORLIFE]

Chevy downsized everything in 1978.
Monte Carlo become junk.
Bean counters started sharing parts everywhere.
The end of GM as we knew them..sad

 

[Octane]

So if this is the case why would they draw a line at the '77 model year ? I may have to call them but I bet they can't give me an answer.

Normally I wouldn't mess with it I don't like modifications and I'm no fan of spacers and adapters. but it just looks crappy being so narrow, I just want to square things up.

They did tho.And the dana 44 can use some of the parts from the corp 10.It causes some confusion among some owners about which they really have,a dana or a 10.

 

[Curt]

The only parts that’s interchangeable between the 44 and 10 bolt is the outers/stub shafts,wheel bearings,hubs.19 spline.

Different widths on 14 bolts those years with narrow versions being on cab & chassis and the widest versions on some vans at 69”,I believe or 67 1/2.

you want the same track width on 4x4s so your rear follows your front and doesn’t slow you down.IMO