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Whats a good 8-3/4??? #565516
12/29/09 12:22 AM 12/29/09 12:22 AM
Joined: Mar 2007
Posts: 12,013
Finally a HUSKER again
Moparnut426 Offline OP
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Moparnut426  Offline OP
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741, 742, 489???

I have 1 of each... And dont know which is the strongest??

Kasey
Re: Whats a good 8-3/4??? [Re: Moparnut426] #565517
12/29/09 01:01 AM 12/29/09 01:01 AM
Joined: Sep 2005
Posts: 2,442
LOWELL IN
Q
QWK_ENUF Offline
top fuel
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Q

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LOWELL IN
742-489-741 last

this is according to quicktree who is considered expert in the 8 3/4

i ran 10.0's at 3235 with a 489 case,spool and one billet cap/stock axles foot brake

my old man 10.90's with 489 case stock caps,spool and yucon axles foot brake

WAXER
Re: Whats a good 8-3/4??? [Re: Moparnut426] #565518
12/29/09 02:35 AM 12/29/09 02:35 AM
Joined: Aug 2003
Posts: 43,232
Bend,OR USA
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Cab_Burge Offline
I Win
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The 742 is the one I consider the best, its pinion stem is thicker at the front bearing seat than the other two It also doesn't need to have a crush sleeved replaced with a pinion spacer instead of the crush sleeve As already mentioned the steel cap on the drivers side is a big plus if you have a lot of traction and HP and torque If you don't you don't really need it

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Whats a good 8-3/4??? [Re: Cab_Burge] #565519
12/29/09 03:36 AM 12/29/09 03:36 AM
Joined: Jan 2003
Posts: 8,016
Polson, MT
DoctorDiff Offline
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DoctorDiff  Offline
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All 3 designs share the same front bearing ID.

The 742 case offers a slightly larger front pinion bearing than the other 2 designs, however.

All 3 versions are comparable in strength if the 489's crush sleeve is replaced with a solid spacer.

Contact info
Re: Whats a good 8-3/4??? [Re: DoctorDiff] #565520
12/29/09 09:11 AM 12/29/09 09:11 AM
Joined: Jan 2005
Posts: 866
Winnipeg ,Mb. CA.
chryco Offline
super stock
chryco  Offline
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Winnipeg ,Mb. CA.
One that looks like this ..................

5695614-IMG_5779.jpg (208 downloads)
Gas is fer washin' parts ....Alky`s fer drinkin' ...Nitro`s fer Racin'!
Re: Whats a good 8-3/4??? [Re: chryco] #565521
12/29/09 09:46 AM 12/29/09 09:46 AM
Joined: Mar 2008
Posts: 1,596
BX, CT, FL.
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B1KILLER Offline
pro stock
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BX, CT, FL.
I believe in either, 9" or Dyna.

5695641-atco1.jpg (161 downloads)
Re: Whats a good 8-3/4??? [Re: Moparnut426] #565522
12/29/09 09:52 AM 12/29/09 09:52 AM
Joined: May 2003
Posts: 13,200
aZLiViN
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J_BODY Offline
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aZLiViN
You're probably looking for something more "street" oriented, but if not, I think we have two "pigs" left ready to go as we put a Dana in our Duster last year. I'm thinking we have a 4.10 and a 4.30, but I'd have to confirm with my dad. The stuff is in SoDak so shipping wouldn't be too bad.
Re: Whats a good 8-3/4??? [Re: Cab_Burge] #565523
12/29/09 11:06 AM 12/29/09 11:06 AM
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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BradH Offline
Taking time off to work on my car
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Quote:

The 742 is the one I consider the best...


Same here. Mine has MW steel caps on both bearings, plus a billet steel yoke, a PowerLock unit (no cone-type Sure-Grip units for me ) and a back brace on the housing.
Re: Whats a good 8-3/4??? [Re: BradH] #565524
12/29/09 11:36 AM 12/29/09 11:36 AM
Joined: Dec 2003
Posts: 5,314
Carstairs, Alberta, Canada
dave571 Offline
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The mp aluminum section is based on the 742 case if that means anything.
Re: Whats a good 8-3/4??? [Re: Moparnut426] #565525
12/29/09 05:18 PM 12/29/09 05:18 PM
Joined: Jul 2004
Posts: 19,318
State of confusion
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Thumperdart Offline
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State of confusion
I run a stock 742 case w/dutchman 30 spline axles and a spool...........so far so good.

72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
Re: Whats a good 8-3/4??? [Re: DoctorDiff] #565526
12/29/09 06:23 PM 12/29/09 06:23 PM
Joined: Dec 2003
Posts: 22,696
Bitopia
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jcc Offline
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Bitopia
Quote:

All 3 designs share the same front bearing ID.

The 742 case offers a slightly larger front pinion bearing than the other 2 designs, however.

All 3 versions are comparable in strength if the 489's crush sleeve is replaced with a solid spacer.



But the 489 has a larger rear bearing? &

a theory in the past that has been floated is that on a 8.75, the pinion under power is trying to deflect at a right angle the ring gear away, and what resists this pressure against the ring gear is the pinion shaft between the front and rear bearings, and some suggest since the 742 shaft does not taper like the 489, it might be stiffer in regards to this possible bending/ distortion, and of course any bending would likely hasten gear failure under load conditions.

Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
Re: Whats a good 8-3/4??? [Re: Moparnut426] #565527
12/29/09 07:28 PM 12/29/09 07:28 PM
Joined: Oct 2004
Posts: 16,479
Canada
CrAzYMoPaRGuY Offline
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Canada
I would be more concerned about a back brace and billet caps to be honest, but my least favorite pig is the 741 case obviously.
I've got a 489 with a crush sleeve eliminator kit in my Coupe.

CrAzYMoPaRGuY
Re: Whats a good 8-3/4??? [Re: B1KILLER] #565528
12/29/09 07:31 PM 12/29/09 07:31 PM
Joined: Oct 2004
Posts: 16,479
Canada
CrAzYMoPaRGuY Offline
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Canada
Quote:

I believe in either, 9" or Dyna.



Stick a stock or near stock Ford 9" rear in a car with power, see if it changes your mind.


I think a stock Dana is the strongest of the three by far, and I would rather use a stock 8 3/4 rear than a stock 9" rear, but that's just me....


There's a huge aftermarket available for the 9", but each and every part costs money...

CrAzYMoPaRGuY
Re: Whats a good 8-3/4??? [Re: jcc] #565529
12/29/09 07:49 PM 12/29/09 07:49 PM
Joined: Jan 2003
Posts: 8,016
Polson, MT
DoctorDiff Offline
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A 489 case does NOT have a larger rear bearing than the 742 version. 742 pinions have a huge stress riser at the base of the front bearing, however.

Pinion design doesn't seem to matter anyway, because the ring gear has proven to be the weak link, regardless.

Check out this link for pinion comparisons:

http://www.moparts.org/Tech/Archive/axle/1.html

Contact info
Re: Whats a good 8-3/4??? [Re: DoctorDiff] #565530
12/29/09 08:51 PM 12/29/09 08:51 PM
Joined: Dec 2003
Posts: 22,696
Bitopia
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jcc Offline
If you can't dazzle em with diamonds..
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Quote:

A 489 case does NOT have a larger rear bearing than the 742 version. 742 pinions have a huge stress riser at the base of the front bearing, however.

Pinion design doesn't seem to matter anyway, because the ring gear has proven to be the weak link, regardless.

Check out this link for pinion comparisons:

http://www.moparts.org/Tech/Archive/axle/1.html



I thought the 489 with a 1.875" pinion used a different size rear (rear being towards rear of car?)bearing then the 742 with a 1.75" pinion and I am asking? You say they are the same?

When you say pinion size/shape doesn't matter because the ring gear is what fails, is there any basis for what is causing the ring gear to fail, and related then, there is then no strenght/durability difference between a 489 & 742?

Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
Re: Whats a good 8-3/4??? [Re: Moparnut426] #565531
12/29/09 08:57 PM 12/29/09 08:57 PM
Joined: Sep 2004
Posts: 192
MI
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RickRoss Offline
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I have a complete rear end with cal tracs and mono leaf springs for a 1969 Barracuda.I think it has a 4.56 gear with a spool and moser axles.It is back braced and has shocks with it.I sold it to a friend and he has no use for it now and will sell it for 1400 that he paid for it.If you need pics PM me.
Re: Whats a good 8-3/4??? [Re: RickRoss] #565532
12/29/09 09:18 PM 12/29/09 09:18 PM
Joined: Mar 2007
Posts: 12,013
Finally a HUSKER again
Moparnut426 Offline OP
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Moparnut426  Offline OP
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Finally a HUSKER again
I have a 489 sure grip in the demon now. Im planning a rebuild of it when the stroker gets done. Its getting a spacer, and a new set of clutches...

My buddy has a 42 Im gonna rebuild for his 65 belvy.

Kasey
Re: Whats a good 8-3/4??? [Re: jcc] #565533
12/29/09 10:29 PM 12/29/09 10:29 PM
Joined: Jan 2003
Posts: 8,016
Polson, MT
DoctorDiff Offline
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DoctorDiff  Offline
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Polson, MT
Basically, the 489 case and 742 case share the same rear bearing bore diameter. Due to the increased size of the pinion shaft, the 489 case incorporates smaller, shorter rollers.

In reality, I don't think there is any meaningful strength difference between the 3 designs.

Too bad the ring gear diameter is not proportional to the pinion shaft and bearing sizes.

Contact info
Re: Whats a good 8-3/4??? [Re: DoctorDiff] #565534
12/30/09 10:46 AM 12/30/09 10:46 AM
Joined: Jan 2003
Posts: 5,894
Florida
Locomotion Offline
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Florida
Somewhere I have heard that one factor in the strength of the ring gear lies in the number of teeth on it. The less teeth, the bigger they are, thus stronger. I don't know if there are other 8 3/4" examples of basically the same ratio having different amounts of ring and pinion teeth.


742 case:

Richmond 4.57 = 32-7
Moser 4.56 = 41-9

But there are other factors too, like metalurgy, quality control, etc. I just go with the better price.

I am trying a set that has been cryo'ed and rem-finished by Jim Bailey. http://www.finishedracing.com/

Last edited by Locomotion; 12/30/09 10:54 AM.
Re: Whats a good 8-3/4??? [Re: Locomotion] #565535
12/30/09 11:21 AM 12/30/09 11:21 AM
Joined: Sep 2006
Posts: 3,011
Sac, CA
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mopowers Offline
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Sac, CA
Quote:

Somewhere I have heard that one factor in the strength of the ring gear lies in the number of teeth on it. The less teeth, the bigger they are, thus stronger. I don't know if there are other 8 3/4" examples of basically the same ratio having different amounts of ring and pinion teeth.


742 case:

Richmond 4.57 = 32-7
Moser 4.56 = 41-9






That's an interesting thought. But wouldn't more teeth spread the load out more?
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