57-62 posi units

[Mike E.]

On the posi "carrier" (I hope that's the right terminology--the part in the center that bolts together--has the cluthes inside--is two round units)--the large bolts that hold those two large round units together--are they by any chance left-hand thread? I have a unit that is rusted, and seem to recall something about left-hand, but am unwilling to trust my memory.
Thanks!

[Mike M.]

Re: 57-62 posi units

mike: been years since i split the carrier but i don't recall the bolts being LHT. Randy's Ring and Pinion might know for sure. they've got a website but i can't find any of their literature today. mike

[Roy B.]

Re: 57-62 posi units "NO"

Same as any bolt you may be removing on a Corvette

[Lee Boyer]

Re: 57-62 posi units

Mike; I am rebuilding a posie as we speek. The 8 -10 bolts you are speeking of could be left or right depending on what year you are working on. I have posted a question about the number of bolts and threads (16-260. The one i am working on ,the bolts turn towards the right to get them out

[Pete Whelan]

Re: 57-62 posi units

Mike,
I still have several left hand thread capscrews for a passenger car posi carrier in my tool box. However, I don't know if the passenger car and Corvette carriers are the same.

You might try using a torque wrench to loosen a capscrew to verify that it is a left hand thread. Don't go more than about 10-15 lb-ft. beyond the torque spec. just in case it is a right hand thread.

Pete

[Tom P.]

Re: 57-62 posi units

Dang!!!!!!
I thought you NCRS gurus would answer this immediatly!
MIKE E,
The 57-59 posi units use right hand thread bolts. The 60-64 (used in pass cars up to 64) units use left hand thread bolts. IT DOESN'T MATTER IF IT IS VETTE, FULL SIZE CHEVY OR 62-63 CHEVY II. THEY ALL USE THE SAME POSI UNIT (and of course, all the 55-64 center sections are interchangeable).
Since you all are not sure about these posi units (Mike M, you really shocked me), I'll provide some additional info (I've been building these things for over 35yrs). The 57-59 units use only 8 clutch plates (4 per side) and the clutch pack is still available from DANA, but it has 10 plates in it. The clutch pack units from DANA today DO NOT have the 2 THIN plates anymore. I have located a machine shop that can surface a thick plate (.090) down to the thinner size (.062). I've taken a stack of used thick plates and had them surfaced down to .062 for use in a 10 plate posi unit. The 60-64 units used 10 plates. YOU CANNOT USE 10 PLATES IN A 57-59 UNIT. The posi case halves and cross shafts for the spider gears for the 57-59 and 60-64 units are NOT interchangeable. If anyone has a 57-59 unit and a 60-64 unit, compare them side by side. You will notice that the "V" of the case and cross shafts are at different angles from one another. So, you have to keep the respective cross shafts/cases together. ALL case halves are machined as a matching set, you cannot mate the half from one case with the other half of another case. When seperating a posi case (or carrier), you FIRST need to mark the 2 halves (I make a punch mark on each half) so that they go back together correctly. Until just VERY RECENTLY, NONE of the internal parts were available. Now, US GEAR reproduces some of the internal parts (gears, cross shafts--------------------AND LEFT HAND THREAD BOLTS!!!!).
Also, both US GEAR and Eaton are now manufacturing complete new posi units for these old rears. The US GEAR unit is about $350 and the Eaton is about $450. NONE of the USG or Eaton guts are interchangeable with the original DANA guts, but the units which they manufacture are a drop-in/bolt-in swap. HOPEFULLY, the people who have been hoarding the original units and charging unrealistic prices for 40+yr old, cracked and stressed units, will now be STUCK with them! This is going to make it easy and practical for people who have cars with a NON-posi rear to convert it to posi.
For those who aren't familiar with converting a non-posi rear to posi, there is one tiny important detail that needs to be pointed out. The case of a non-posi rear has a gusset cast in it which a posi case case DOES NOT have. In order to drop a posi carrier into a non-posi case, you must first cut away a portion of this gusset. I use a die grinder and cutoff wheel to do this and then smooth it up with a small grinding stone. Since this will produce a lot of metal particals inside the case, the pinion needs to be removed so that the bearings don't get full of particals. Converting a non-posi rear is easier than, well, let's just leave it at that.
Mike E, hope this helps.

[Terry D.]

Re: 57-62 posi units

Tom
It is greatly appreciated by those of us who aren't experts to hear from those of you who are. Any chance of getting a picture posted to show the difference in the cases? I really think a few of you who have been around Corvette's for years should get together and write a book about interchanging parts, shortcuts and other bits of information NOT found in the Assembly Manual or the NCRS Judging manual. It would be greatly appreciated I'm sure.

Terry

[Tom P.]

Re: 57-62 posi units

I have several posi rears set up and as far as I recall, only one is a 57-59 type. When I get a chance, I will try to pull them out and take comparison pictures. As we speak, I am in the middle of rebuilding a 57 front crossmember/suspension and 3 T-10s for a customer. And yesterday my 18yr old son broke the engine in his 68 Chevelle, so today I have been scrambling to get an engine put together for his car.