Help! Rear Axle info needed....

[absintheisfun]

I have a 63, and as far as I can tell, it is stock. I want to put in a posi.

SO the questions-

What spline are the factory axles?

Will a modern 12-bolt posi unit fit? I noticed the shape of the pumkin is a bit different.

Thanks!

[blue64c20]

Are you sure its not a 10 bolt rear end in it? I have a 64 c20 and its got a stock 10 bolt rear end with an 8 lug pattern

[Captainfab]

The '63 & '64 12 bolt truck rear differentials have 17 spline axles. So the '65 and newer posi units will not work in your differential without changing axles also.

[absintheisfun]

Thanks for the info. Though it is unfortunate as I was looking to do a quick swap!

[First66]

Originally Posted by Captainfab

The '63 & '64 12 bolt truck rear differentials have 17 spline axles. So the '65 and newer posi units will not work in your differential without changing axles also.

Not looking to hijack this thread but a quick search for the word "spline" led me here, and you seem to be the best person to ask about this. Would a 67-72, 5-lug axel fit my 66 with stock rear end?

[Captainfab]

As long as your '66 has the trailing arms, and the donor does as well, then yes it will be a direct bolt in. However, be aware that the '71-'87 5 lug differentials are 1.5" wider than the differential currently in your '66. This may or may not be an issue, depending on your tire and wheel size.

Originally Posted by First66

Not looking to hijack this thread but a quick search for the word "spline" led me here, and you seem to be the best person to ask about this. Would a 67-72, 5-lug axel fit my 66 with stock rear end?