Technical 8.5 10 bolt posi cutch specs question

I just picked up a 70's vintage 10 bolt posi, and I've been digging into it to check it out. Everything looks good and clean, but when checking the clutches I found what may be an issue. I know that you can still spin one axle when the other one is locked in place(a pry bar between studs braced on the ground), but don't know what the break away torque should be. I'm measuring just under 20 lb/ft. Seems kinda low to me, but I have no idea what it should be. Can anyone here give me an idea what it should be? By the way, this is the odd ball S style tension spring model.

 

If memory serves, my D44 with new clutches should be 70? Ft/lbs. service (again memory) was 30 ft/lbs.

I locked one side, made a plate that slipped over two lug nuts, welded a socket in the center for my torque wrench.
The numbers I recall are rotational numbers, not break over numbers.

 

I didn't make anything special to check it, just put a lug nut on one of the studs and used that for my torque wrench. I knew it wouldn't be accurate, but didn't think it would be that far off. I can make a plate up to do what you did, but won't be able to for a couple days. Hope to get some more input here in the meantime.

 

in 1973, Chevy specified 70 ft lbs for new unit, no less than 40 for used unit. Using a torque wrench, like you did.

 

My book states 70 ft. lbs. new and no less than 40 used. That's the torque to rotate the axle.

 

If ya lag until the weekend, I can pull out the manual (64, GM pickup) I used when I rebuilt it. My D44 had clutches, pretty sure a spring or two? But mine spun like a merry go round.
So all came apart.

 

Well, part of my memory is working, and I also saved “the hunt”

 

Guess I need new clutches, but I kind of figured as much . They aren't easy to find for my style posi. I found one place that carries them. $200 shipped. I guess that's not too bad considering everything else looks good.

 

Wouldn't it require less torque to turn being further from the center of the axle on a lug, someone else can do the math. You might actually have more than 20 lb/ft at the center of axle.

 

The difference will be a relatively small amount....not half.

 

Just get yourself some .005" thick shim stock, cut a donut shim to go behind the clutch pack on each side.
Done it several times, tightens a loose Eaton posi right up. If you go to .007" shim stock it will set one up quite tight (drag race use) but it will chatter when hot during tight, slow turns even with friction modifier in the oil. .
As far as I know, every original 8.5" 10-bolt posi differential that was OEM from 1971 to at least 1982 was the S-spring type.

You won't get a true torque reading using a lug stud because the stud is on a 2.375" radius from axle centerline. It would be no different than if you used a torque wrench with a reach extension and socket on a bolt.....the distance from center is a force multiplier.
Example : With a 2" wrench and the 2.375" bolt pattern radius, 20 ft.lbs on the wench actually applies very close to 25 ft.lbs to the axle.
How To Calculate Torque Wrench Extension: A Complete Guide For Accurate Torque Measurements | Tools Advisor

If those new clutches are the carbon fiber version, I wouldn't use them. The break too easily.
Metal clutches only is my recommendation if you do replace them.

 

If you shim it like was suggested above, I was always told you can get a little more “grab” out of worn clutches if you mix them up on re***embly.

 

Kind of what I was thinking, but I can fab up a plate easy enough. I will do that as soon as I can get to it.

 

A shim would be interesting solution, thanks! As far as the spring type, I can find lots of info on the coil spring design, where there is little on the S type, especially when it come to clutches. Speaking of which, the only ones I can find are indeed carbon, bummer. Here is the link to the kit:
https://www.ronsmachiningservice.net/cart.php?suggest=a9b7482a-4c35-4a74-936e-6a747275efff

 

Something that has occurred to me just now is that the oil looking so nice and clean could mean that it has been replaced recently. If that is the case, maybe they didn't put any friction modifier in with it. Would that cause the clutches to slip? If it does, would taking the clutches out and cleaning them up and soaking them in friction modifier help?

 

but if you put the wrench on it perpendicular to the way you're thinking, the length of the torque wrench won't be any different, and the reading will be correct. And you can also put the wrench on so that it crosses over the center of the axle, then it will be off the other way (reading higher torque than it's actually getting).

Since the minimum spec is 40 and he's at 20, it needs some work.

Don't expect friction modifier to make it tighter...

 

I guess I can try the shim method then The only clutches I could find are the carbon ones that Ericnova72 does not recommend. Does any one here know where to get a better clutch kit for the S type posi?

 

Years back I’m pretty sure I got mine from Randy’s Ring and pinion. Unsure if still in business, this was late 90’s, early 2000’s

 

This place?
https://www.randysworldwide.com/
I checked the site, but unclear if the clutches they offer are for my style posi

 

Doesn’t look like the same place. Besides the name, I seem to recall he was in Northern California.
As I mentioned, it’s been well over 20 years. Very possible he’s not there, sold out etc.
I recall when I located him, I dialed the phone and he answered.
The website you posted seems much larger a business than I would have thought it was at the time.

 

Oh well, I guess the search for a good clutch kit continues

 

EDIT:

After re-reading the ad for this kit, it seems they are carbon steel, not carbon fiber after all!