12 Bolt Posi rebuild - steel or carbon discs?
04-29-2013, 11:33 PM
#1
12 Bolt Posi rebuild - steel or carbon discs? I am rebuilding the Eaton Limited slip differential in my Strange 12 Bolt.
It was originally equipped with carbon fiber discs.
I see there is a steel disc option availiable too from EATON
My only experience sofar has been with theese carbon fibre discs and I do not know what to expect from the steel disc kit. I have not been able to find any information on it either. Would it be a better, more durable and better gripping option?
Anybody here used both and can tell me the difference?
Thanks for any input.
Steel kit and carbon kit:
It was originally equipped with carbon fiber discs.
I see there is a steel disc option availiable too from EATON
My only experience sofar has been with theese carbon fibre discs and I do not know what to expect from the steel disc kit. I have not been able to find any information on it either. Would it be a better, more durable and better gripping option?
Anybody here used both and can tell me the difference?
Thanks for any input.
Steel kit and carbon kit:
Last edited by RGSS; 04-30-2013 at 12:03 AM.
04-30-2013, 06:08 PM
#3
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I rebuilt my eaton unit with "snowflake" steels from Ratech. They were much more aggressive than the original carbon fiber. They were however much quieter while slipping.
04-30-2013, 11:05 PM
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Yup. I know some say they are junk and tend to break...probably will under the same conditions that would destroy/warp a solid plate. But I look at it from a street/strip point of view. For street driving(low speed) fluid can easily get onto the faces which will nearly eliminate the chance of chatter while still feel aggressive. High speed or during a burnout the fluid can sling out and provide a better chance of lock up when you want it most. The CF clutches it came with did not last very long and once they wore out it made a god awful noise around every turn. BTW I used Lakewood BFL 80/90 with no additional additive when I changed out the CF clutches...worked very well.
04-30-2013, 11:26 PM
#6
I found a good thread on a Corvette forum bashing the "new" carbon fibre friction discs. There was one particular post stating that a brand new carbon fiber clutch pack went down the drain on the first pass behind a 600 HP motor:
According to the box, they are Eaton's and I'm sure the supplier is aware of Tom Watt. Don't get me wrong, I like the new Eaton carriers just not the gears or clutches in them.When I first heard of these a few years ago a friend had them installed in his car and they failed. I asked what was done to correct the problem but his shop didn't say, I'm guessing the steels were installed. When I asked Kenny @ Tom's about them he said they used a set on a 600 HP drag car and they poured out of the drain after the first run. I thought he was kidding!
Last edited by RGSS; 04-30-2013 at 11:31 PM.
04-30-2013, 11:43 PM
#7
This is an extract of a vendor's catalogue that sums up the clutch options availiable for the 12 bolt:
I am decided to try out the 18 solid disc and plate set. I had already bought a carbon replacement 
CHEVROLET 12-BOLT EATON POSI PARTS
We offer all 3 styles of clutch packs for Eaton type
posi's (all sets include 4 posi clips). Posi shim set
now included in Part #C 12-PP 18S & 14CF
Posi Plates
18 Solid Disc and Plate Set "My Favorite"
Part #C12-PP 18S Price $110.50
18 Slotted Disc and Plate Set "Current
Factory Rep"
Part #C12-PP Contact Dealer
22 Solid Disc and Plate Set
Part #C12-PP22 Price $126.50
New 14 solid Pyrolytic Carbon Disc's.
Part #C12-PP14CF Price $ 126.50
We offer all 3 styles of clutch packs for Eaton type
posi's (all sets include 4 posi clips). Posi shim set
now included in Part #C 12-PP 18S & 14CF
Posi Plates
18 Solid Disc and Plate Set "My Favorite"
Part #C12-PP 18S Price $110.50
18 Slotted Disc and Plate Set "Current
Factory Rep"
Part #C12-PP Contact Dealer
22 Solid Disc and Plate Set
Part #C12-PP22 Price $126.50
New 14 solid Pyrolytic Carbon Disc's.
Part #C12-PP14CF Price $ 126.50
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05-01-2013, 07:28 AM
#8
Some more info I found on the carbon and steel discs:
I am writing it down in case anyone should need the part numbers. I am going with the 18 disc set and 400# springs. I will come back after installing it with my feedback.
I am writing it down in case anyone should need the part numbers. I am going with the 18 disc set and 400# springs. I will come back after installing it with my feedback.
The 14 disc set is the new carbon fiber set. They are good for a street car, but for drag racing I prefer the steel clutches. The 18 disc set (EATON PN 29403-00S) is good for street/strip use and the 22 disc set(EATON PN 29402-00S) is good for drag racing. The 22 disc set has thinner discs in it and there can be issues with lots of street use, plus they tend to chatter more. The 400 pound springs with the 18 disc set should be good for what you want to do.
05-01-2013, 03:45 PM
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05-01-2013, 04:22 PM
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Well I cant give any numbers in terms of lbs/ft, I can only say that it felt much tighter than with the CF's...in fact the first few turns made before the oil had a chance to warm up it would scrub the inside tire, something it never did with the CF disc even new. The steering felt heavier once it did warm up. This was reusing the stock eaton yellow springs(400lbs).
