Re: how to identify 742 or 489 aluminum case for rear end
[Re: Supercuda]
#1260863
07/24/12 07:26 PM
07/24/12 07:26 PM
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Joined: Dec 2005
Posts: 4,261 State of Fascism
52savoy
master
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master
Joined: Dec 2005
Posts: 4,261
State of Fascism
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Quote:
Quote:
There was time(1960s-early '70's) when a lot of dragsters used 8 3/4's and cases were made out of different materials.. I would guess they were all 742 cases because the pinion isn't tapered, which is the weak link of a 489.
The weak link isn't the taper so much as it is the crush sleeve that can get loose with repeated hard usage. A solid shim replacement setup will cure that.
I'll stick by my comment unless someone can prove me wrong.. The spacer is one of two weak links on a 489,not counting ring gear diameter or deflection. 742's have(or used to) a much larger gear choice because of their strength(pin.stem diameter). Chrysler's "Performance Parts" pro gears were for a 742 case for a reason.
your turn..
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Re: how to identify 742 or 489 aluminum case for rear end
[Re: Supercuda]
#1260866
07/25/12 05:18 AM
07/25/12 05:18 AM
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Joined: Dec 2005
Posts: 4,261 State of Fascism
52savoy
master
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master
Joined: Dec 2005
Posts: 4,261
State of Fascism
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What ???? Removing metal doesn't make the stem stronger unless you've found out about some Area51 process that defies logic and.....metal.. The pinion is called "tapered for a reason. At just one point(1 7/8") is it bigger than a 742(1 3/4"). A 742 is straight cut to the yoke, just slightly smaller dia. than a 489 and therefore stronger. Now if Chrysler in hindsight decided to make the 1 7/8" machined straight all way over to the yoke we would have something. Anyone can believe what they want but facts ARE FACTS. Been doing this mopar thing going on 50 years so I don't need to make it up... and I doubt under any circumstances that I could convince you but no problem. If you make it my way some time I'll start up the grille and we'll go my shop to sort it out while the Texas BBQ is smoking.. comparison shot..... web page I remember in the 70s Chrysler started getting negative feedback from racers who were breaking the large stem pinions in half. They put out bulletins on that subject and recommended racers use the non-tapered 742 case. The story is in the mopar bible. I happened to have worked for local stock and super/stock racers Starkey and Christian and their expierience went back to 1959. Even though I knew of Chrysler's position, it was the first time I got it from racers but with more details... but it's ok... do your own thing or go Dana.
Last edited by 52savoy; 07/25/12 07:19 AM.
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Re: how to identify 742 or 489 aluminum case for rear end
[Re: 52savoy]
#1260867
07/25/12 09:56 AM
07/25/12 09:56 AM
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Joined: Dec 2003
Posts: 22,765 Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,765
Bitopia
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Regarding strength of 742 vs 489 stem, if someone could PROVE to me that it fails more then say once in a million, I'll join the argument of arraigning the deck chairs on the Titanic. My suggestion, argue something more worthy.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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