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489 or 742 posi unit for street and strip

Posted By: saukvillage

489 or 742 posi unit for street and strip - 11/02/10 02:47 AM

I have two posi units a 489 and 742. I would like to know the difference between the two and which one would be considerd the stronger or more reliable unit for street and strip.
Posted By: Neil

Re: 489 or 742 posi unit for street and strip - 11/02/10 02:51 AM

The 742 is the better of the two versions.
Posted By: patrick

Re: 489 or 742 posi unit for street and strip - 11/02/10 02:55 AM

489 is most likely an auburn style (cone), the 742 an eaton posi style (clutch)....I haven't had a cone style last longer than about 10k miles before it went open....

if buying new, I'd get one of the eaton torsen style, unless you're using a very high torque motor and verrry sticky tires (aka slicks) and your suspension hooks.
Posted By: fourgearsavoy

Re: 489 or 742 posi unit for street and strip - 11/02/10 03:18 AM

Quote:

The 742 is the better of the two versions.


And a lot easier to set up
Gus

Attached picture 6280492-burnoutpicturegus.JPG
Posted By: RobX4406

Re: 489 or 742 posi unit for street and strip - 11/02/10 03:54 AM

Quote:

Quote:

The 742 is the better of the two versions.


And a lot easier to set up
Gus



Use a crush sleeve eliminator and the 489's are just as easy.
Posted By: JohnRR

Re: 489 or 742 posi unit for street and strip - 11/02/10 01:54 PM

Quote:

Quote:

Quote:

The 742 is the better of the two versions.


And a lot easier to set up
Gus



Use a crush sleeve eliminator and the 489's are just as easy.



But it will still have the POS sure grip
Posted By: MoparforLife

Re: 489 or 742 posi unit for street and strip - 11/02/10 02:33 PM

Quote:

Quote:

Quote:

Quote:

The 742 is the better of the two versions.


And a lot easier to set up
Gus



Use a crush sleeve eliminator and the 489's are just as easy.



But it will still have the POS sure grip

Not necessarily. As you know the sure grips are interchangeable between all cases and a lot have been changed over or it can be easily changed over.
Posted By: Paul_Fancsali

Re: 489 or 742 posi unit for street and strip - 11/02/10 02:55 PM

Back in the 60-70s Mopar mechanic's use to say the 742 clutch sure grip was junk and the cone lasted forever !Well 45 years later I'm finding they don't last forever but frankly after that long who cares? I'm using cone one that on its way but when it goes for good I'll replace it.
Posted By: b54406barrel

Re: 489 or 742 posi unit for street and strip - 11/02/10 04:34 PM

Quote:

Back in the 60-70s Mopar mechanic's use to say the 742 clutch sure grip was junk and the cone lasted forever !Well 45 years later I'm finding they don't last forever but frankly after that long who cares? I'm using cone one that on its way but when it goes for good I'll replace it.



Good to know I've got 5 years left! I've been beating the crud out of the 6bbl car 489 for 40 years.
Posted By: 383man

Re: 489 or 742 posi unit for street and strip - 11/04/10 11:26 PM

Do like I did as when the sure grip goes south put a Detroit Locker in it. Ron
Posted By: imfixinmopars426

Re: 489 or 742 posi unit for street and strip - 11/04/10 11:30 PM

if ring gear bolts are on same side as diff bolts its a cone,different sides its a clutch type,use the clutch in either cases,cones suck.
Posted By: dOoC

Re: 489 or 742 posi unit for street and strip - 11/04/10 11:54 PM

ANYONE ever try the AIR-locker ?
Posted By: pnypwr

Re: 489 or 742 posi unit for street and strip - 11/05/10 02:20 AM

iv put in serveral arb air lockers..they are more of a off road locker, and less like a limited slip, meaning when they are locked they arelocked! if replacing id recomned a detroit true trac, the street manners of an open rear but locks up under slip...its alot better than a stock suregrip hands down
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