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What is the actual name of the '57 rear end? Does it have a name? Does anyone make a mini-spool for it? Is it worth putting in a spool or will it break something easy from a bit of abuse? Is axl failure common? To find the ratio do i count how many times the pinion goes around in relation to the hub, then what?
Any help apprieciated
Dan
 

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Dan: I don't know if there is an actual name for the '55 -'57 rearend, but I've heard them called "pumpkins" and "hogsheads". Not sure if there is a mini-spool available but I've had real good luck with the posi units.With proper gearing they're good for around 500hp. Only had 1 axle break and that was shortly after put in 4:56 gears, and it showed signs of an old crack at the wheel bearing flange. Don't know how old the axle was as it came with the car when I bought it in '70. Any way it depends on how much power and abuse you intend to dish out. Hope this helps.
 

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To expand on the strength factor, the Eaton will probably be stronger than an original posi unit because it is BRAND NEW, as opposed to 40+yrs old, stressed and possibly cracked. The original posi units were made by DANA and were 2 halves bolted together. It is not uncommon to see very small to big cracks along the area of the bolt holes that hold the two halves together. A brand new Eaton, first of all, is a one-piece posi unit. Second, it is just that, BRAND NEW, never stressed and no cracks.
I've said this many, many times before and I'll repeat it, Keep in mind that this style rearend was FACTORY installed behind 63-64 425hp/409s as well as solid lifter, tripower 348s (they had just a little bit of grunt)! And yes, they did break a few of them-----------------------BUT LOOK WHAT IT TOOK TO BREAK 'UM!!!!!!!!

The above is borrowed from a person I think of as friend.

"Tom Parsons"
 

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A standard trans with clutch is much harder on the rear axle than an automatic trans. The age of these old differentials and the abuse they have had will determine how long they may last. If it is not noisy I would not worry to much.
Dave
 

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I agree with MikeKy55 - Mr Parson said it best! I have had no problems with the DANA have been beating on them for years.:D From 488's to 308 never broke a unit just axels. :mad:

Dennis
 

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I used to break stock rear ends on a regular bases with my '62 Corvette fuelie, 4 speed. Sometimes axles, sometimes spider gears, and other times it was so bad I couldn't figure out what broke first spiders or ? On my last 4:88 rear I built I added Moroso cradle straps over the carrier bearings which is supposed to keep the journal from cracking letting everything get out of wack and grenadeing 4 a lack of better wording. After the fuelie I built a stroker 4 the Vette, added more rubber to the road and still no problems with the rear gears, can't say that about the axles though! Lon
 

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Hey CAT,:p what E.T and MPH where you running back in the day?.. I agree cradle straps are a must.

Dennis
 

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If you have the pumpkin out of the axle housing you divide the pinion into the ring gear for the ratio. If it is in the car and it is an open (not posi), you must hold one wheel and rotate the other two revolutions and watch the pinion flange for how many times it rotates and that will be the ratio.
 
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