1964 12 bolt posi interchange?

[aerotruk63]

According to my Hollander Interchange, only 63-66 posi units are interchangeable? Do no other years bolt in?

[turp mcspray]

It may be a Dana unit instead of an Eaton. I pulled a Dana posi out of a 64 truck 12 bolt, many years ago. Back then I looked for parts to rebuild it, and could not find anything. I don't know when they made the switch to Eaton posi units, but in 65 when they came out with the car 12 bolts, they all used Eaton. Every truck I have seen from the mid 60's and up. have used the Eatons. They will interchange with each other. I had a Dana posi laying around once upon a time, and put in a 72 that I had.

[Captainfab]

Any posi unit from a truck 12 bolt will interchange into the housing. The difference in your '64 will be the 17 spline axle shafts, unless someone has changed them. Starting in '65 the axleshafts had 30 splines. To my knowledge the Dana posi units were available in 17 splines only. At least the ones I have are all 17 splines. Starting in '65 the Eaton posi units were available. When looking at a Eaton posi unit, be sure to get one of the correct series for the gears you plan to run. The 3 series are for the 3.42 and lower numerically, and the 4 series are for the 3.73 and higher numerically.

[turp mcspray]

I was unaware of the 17 spline axles. Both of the Dana units I had were 30 spline units. The first one I had, I pulled from a 64 truck. I put it in a car 12 bolt and genaded it. Thats how I found out parts for it were unavailable. The second one I had, I got at a swap meet, and don't know what year it was, but I put in a 72 I had at the time. Thanks for the info Cap'n!

[raycow]

Turp, are you saying that a TRUCK 12 bolt posi will fit in a CAR housing? If yes, are any mods needed to make this work?

Ray

[turp mcspray]

Some will. I have used truck posi units in car rears more than once. The truck units have two large windows in the case, where car units have one. The car ones are stronger.
I did not have to modify anything. I don't know that they all will work.

[raycow]

Thank you, Turp. This is why I like this board so much. I can learn stuff here that I never see anywhere else.

Actually, I was thinking about the reverse, using a car posi in a truck. A lot of good stuff is made for the car rears because they are popular for racing.

Ray

[aerotruk63]

Allrighty then as long as the axle splines are the same as what I have a 12 bolt out of a car will fit as well?

[turp mcspray]

I have found that the car units will NOT fit in the truck rear. Seems like the car unit has a squared off "bump" on the case that hits the truck housing. It has been awhile since I have done any swapping, so I don't remember all the details off the top of my head. It may have been just a certain series carrier that was swappable. I've got a guy that wants to buy a posi from me, so I will do a little research when I get them dug out, and report back on the issue. Someone else may also know some of this info as well.

[turp mcspray]

I have found several references to the truck 3 series posi, with casting number 2212, as being car 12 bolt friendly. I put together a 12 bolt in my 65 elcamino with 3.55 gears and a truck posi. I would have to pull the cover to check, but that is probably the posi that I used.