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AMC 20 PowerLoc Posi Discs Question

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kcsamc View Drop Down
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    Posted: Jun/23/2014 at 10:22pm
Maybe this subject has been discussed in the past, but my search through the posts here didn't yield anything.

What I am looking for: First hand experience with rebuilding the PowerLoc unit with new "replacement" Dana posi clutch disc pack. Those of you out there that have gotten your fingers dirty with the replacement kits, and have even taken your cars out and beat on them for an extended period of time afterwards.

Did you notice that the replacement kit is not the same as factory original / NOS replacement kits? Directly from the 1969 TSM:


Opening up my original SC/Rambler unit verified what the TSM calls for both in disc types / quantities / stack order:


Reviewing the replacement kit from Dana (no instructions, no mentioning differences from factory original, and no information on how to stack these non standard parts:


At the end of the day on the rebuild project, two degreed engineers stood there and said there was no way we were going to insert anything but the original style components into the AMC 20 PowerLoc rear. Not having a second Belleville washered disc in there has to be asking for a slippage condition, and considering the time / money and aggravation of going that deep back into a rebuild for something like this it wasn't worth the risk, so we didn't use it.

However, for the sake of all AMCers that come behind me, I need to know if anyone knows the reason why this new kit is not the same, and what the real life impact has been by using it. I don't trust it and I'm looking for input. Also considering how to potentially approach Dana directly on this.

Experienced responses please!
Kevin Shope
1964 Classic 660
1964 Amb. 990H
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amc67rogue Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2014 at 11:30am
The powerlock unit was also used in early 10 bolt chevys , early olds & pontiac , mopar 8 3/4 . Some of the early units used all flat discs . The dished style puts preload in the unit , the flat ones don't have the preload ,they get loaded by the four spider gear assembly trying to ride up the ramps in the case. The dished one are load by the dished plates and get even more load from the same ramps . In my Rogue I put the dished plate between the flat and dished disc , gives double the friction area . Look at a view of the 8 3/4 mopar unit . What do you're old ones look like ,all smooth or galled?  I've never used any replacements mine are still the OEM discs.  I hope I didn't confuse you any more .  
Keith Coggins 67Rogue X code
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_P Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2014 at 10:01pm
I have posted on this before... if you measure thicknesses of the components you'll see that some are thicker in the new Dana stuff vs what was OE to help make up the difference. Not ideal, but....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kcsamc Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2014 at 10:33pm
Steve can you point me to your old post? Thanks. We saw what they were doing and didn't agree with it from an engineering perspective. The space may be taken up but the load is not.
Kevin Shope
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Airdrie AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jun/25/2014 at 11:02pm
I've run into this before, I reuse the dished disk and thin plate if not galled badly and use the thick dished plate, flat disk and thick plate from the kit. If you measure those pieces they are the same thickness as the originals. What I do prior to installing the ring gear is clamp an axle in a vise and slide the trac loc on, slide the other axle in and check the breakaway torque required for the unit to slip with a torque wrench. I can't remember the spec off the top of my head but you'll find it in the TSM.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kcsamc Quote  Post ReplyReply Direct Link To This Post Posted: Jul/16/2014 at 10:11pm
I appreciate those who have posted. I decided I couldn't take the status quo on this issue as I know it is or will impact someone's rebuild in the future, plus I needed to replace an NOS (real) kit we used to build my rear recently. I will do a full writeup on this in a separate vendor section, but I wanted to conclude this thread on a positive note.

All but my thin plates were trashed from my rear, I could not re-use the thick dished plates; I could have used the thin flat plates.

I followed a hunch, and a note mentioned here about the 8 3/4 Mopar rear and hit pay dirt, and I learned a few things along the way. Long and short - the 8 3/4" rear Powerlok has the IDENTICAL disc plates as the AMC 20 Powerlok. And there is a reasonable cost source of the 100% correct kit available (cheaper than the wrong kit offered in the AMC vendor community).

I spent some time in email and direct discussions with the authority on 8 3/4" rears and who also has some knowledge of the AMC20, so I got even more info than I started out to find (always a good thing). Turns out the kit being sold in AMC circles is the wrong Dana 44 kit. We are lucky that the 8 3/4" uses these same disc plates. I ordered a kit and did a full comparison to the original kit. The only thing I could find was that the dished plate new was a little more "bellevilled" than the worn out original - not a problem. Everything else - dead on.

Picture of AMC 20 pieces (bottom) vs 8 3/4" Mopar (top):


Buy with confidence! $75 + $8 shipping
www.doctordiff.com
406-883-4772 (ask for Cass)

I will address a little of the rest of the 8 3/4 vs. AMC20 in a product/vendor review posting, but for now, there is no reason to mess around with any other kit out there. This is the best one, and at a great price.
Kevin Shope
1964 Classic 660
1964 Amb. 990H
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vezzzzzzz Quote  Post ReplyReply Direct Link To This Post Posted: Jul/18/2014 at 7:15pm
Great way to sum it up!
Jeffry
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