63-79 3 series posi cases obsoleted

[Gary R.]

FYI,Just public service announcement for those of you with original 63-79 vettes, primarily the 63-68's which are prone to cracking the posi cases, GM is no longer stocking new bare cases. I would say 80% of the 63-68 diff's I get in have cracked posi's in them. The only options now will be using a new loaded posi, I would only use the bare case not the internals on these or try to find a good used posi case. You really have to check the used ones as well to be sure they are not cracked.Here is what you want.

[Stuart F.]

Re: 63-79 3 series posi cases obsoleted

Does this mean I should stop power shifting my original 63 w/3.36 posi???
Thanks for the heads up.

Stu Fox

[Gary R.]

Re: 63-79 3 series posi cases obsoleted

Does this mean I should stop power shifting my original 63 w/3.36 posi???Thanks for the heads up.Stu Fox

Hi Stu,Well if your 63 does still have the Dana posi good for you. They weren't too good to begin with but on occasion I do see them come in. Even if not broken parts are obsolete for them. In fact a lot of placed won't take them in to rebuild because of this. I would say most 63-64 diff's I get in already have an Eaton posi, usually the first design. To rebuild an 63-64 and some 65's the R&P set is one that uses a 17 spline, poorly designed pinion so they should be replaced which also mean the pinion yoke will have to be replaced because the new gears are 30 spline. So you add up the old Dana posi, gears, and yoke and you end up building just the housing maybe reusing the axles. I do them all the time but always explain what needs to be done first.Good luck with yours, watch 2nd gear although you can't be as hard on the car as my son is. His last track day was a new one on me, he completely sheared through the inner & outer solid spicer LH u-joints in his near 10 sec '75 vette.

[Stuart F.]

Re: 63-79 3 series posi cases obsoleted

Gary;

Mine is a July 9/63 build with a little over 46k on the ticker (I bought it new). I had to have a leaking pinion seal replaced after its' longest storage while I was out of the country in SEA. Other than that, I have not noticed any problems. When I last used it up north in the snow (around 1976), the posi seemed to work properly. Since then I have not had need to test it, i.e. I don't do burn outs off the line with an L-76 and 3.36 final. I do pull a mean 2nd now and then - enough to get a squeal, but my half shafts still seem tight with normal amount of play (recall changing joints and a cracked spindle in around 1992). I'm learning to calm down (have to) and limit my rides to Sunday mornings to keep the traffic away from my gas tank, but I still feel the need now and then to use it as my cardiac booster.

When the need arises for me to repair or upgrade, I'll sure keep you in mind or have it noted in my final wishes, Ha!

Thanks again for the information. I'll be certain to share it with my son as well (he now has a 62 fuelie, a 69 L-89, an 82 Collector, a 93 40th ann, and an 08 PC.).

Stu Fox

[Gary R.]

Re: 63-79 3 series posi cases obsoleted

Stu,Keep on enjoying the car and as long as you're not abusing it then who knows, that posi could last many a mile until you celebrate your 100th BD in it!