'64 posi unit

[Tom L.]

My brother-in-law is in the process of replacing his chassis with a new one from Vette products. While it is apart he is going to rebuild the rear. I'm aware that the early posi units are not very good. The way to tell is the size of the window, correct? Or are there other ways to identify them.

Can someone post pictures, other methods of identification or dimensions of the window so he knows what he has? Thanks!!

[Wayne M.]

Re: '64 posi unit

..... I'm aware that the early posi units are not very good. The way to tell is the size of the window, correct? Or are there other ways to identify them.

Can someone post pictures, other methods of identification or dimensions of the window so he knows what he has? Thanks!!

Lynn -- Don't be surprised if when the cover is removed, the Dana posi has already been replaced [ie. good news].

I don't have a Dana for pics, but here's a few of the 1st design Eaton unit, for starters. You haven't mentioned the rear end ratio (means could have a 3-series or 4-series posi carrier) . Characteristic is the small (postage stamp sized) window on one side. For a 3-series the cast # will be EDB 30117 (1st pic). If a 4-series 1st design, the cast # will be EDB 30175, or, the last 3 digits cast into the ring gear side of the posi case (pic # 2, is a Jan '64 posi with a 1st design 4-series posi installed).

If 2nd design Eaton {the strongest}, the postage stamp window is replaced by a much larger one. 4-series will be cast EDB 32298; if 3-series, EDB 32297. I'll dig out some pics in a while.

[Wayne M.]

Re: '64 posi unit

Here's 2 pics of the 2nd design Eaton posi case; this one's a 4-series. You can see the postage stamp-sized window of the first design has grown (pic on left; pic on right is after rotating posi case 180 degrees).

[Gary R.]

Re: '64 posi unit

As Wayne stated, the 63-64 used the Dana posi when so ordered. They were weak and many are gone by now but I still see them. You can't get parts for them and you wouldn't want to build them even if you can. They have long thin springs on them compared to the Eatons.

The 1st design Eaton were better but not by much. I think 1/2 of what I see are cracked.

The 2nd design were much better, they didn't crack as much as the earlier ones and were generally exposed to more power as the BB cars came in and the cars were built stronger then stock.

The spiders used in the 65-70 were not as good as the 71-79 but the clutches were solids and much better then those snowflakes used in 71-79.

If you're building a mild cruiser then a stock 1st design is ok to use. Be sure it's not cracked.

The new loaded are ok for a mild car as well but I'd never recommend them.

The best to use are the ones build to the application.

Here is a stone stock 64 posi. I removed it and it wasn't broken but it ended up a paperweight.


Keep in mind if you do have one of these then the ring gear and pinion yoke are also obsolete and you'll have to upgrade them.

If you want more pictures let me know, I don't want to post too many.

[Tom L.]

Re: '64 posi unit

Wayne and Gary, Thanks! just what I was looking for. Just like his problem with the frame, he won't be happy. He told me he already ordered new gears for a '64. He wanted to upgrade from 3.08's to 3.55's.

When looking for cracks, will they be obvious or is magnafluxing required?

[Wayne M.]

Re: '64 posi unit

....When looking for cracks, will they be obvious or is magnafluxing required?

Let me add to that; Gary, do you use dye penetrant to locate ? Are cracks usually found starting at the small window and/or where the big pin anchors in both sides of the case ?

[Gary R.]

Re: '64 posi unit

You can get them fluxed if you like but all I do is clean them good, shoot some brake cleaner on them and blow them off with low press air. If there is a crack it will stay wet and show up. Look at the radius of the windows,at the side holes,and sm window. The 1st design cases have parallel seams that lead to the cracking, the 2nd design has a staggered seam that is stronger.

Lynn- if you're going to use 355's you might want to contact me. I would post the info I know but some complain about my posts so I'm going to cut back on info I give out. If you choose the wrong brand you're going to have a headache. If you have someone do it and they use the brand then you won't know unless they're sharp.

[Tom L.]

Re: '64 posi unit

Thanks gary, from your post I assume there is an issue with using 3.55's. Is this true jsut for the original 64 posi or the later ones as well.

Thanks again, I'll pass the info along.

[Wayne M.]

Re: '64 posi unit

Thanks gary, from your post I assume there is an issue with using 3.55's. Is this true jsut for the original 64 posi or the later ones as well..

Lynn -- please do post what your friend finds after dismantling his differential, so that the rest of us might learn and/or comment. If he's going to install 3.55 GM gears, just off-hand, (as a general comment) I can't see why this would be a problem.