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8 3/4 third member question-what is wrong
#1469597
07/18/13 02:25 AM
07/18/13 02:25 AM
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Joined: Jan 2009
Posts: 903
Oregon
rtplumcrazy1
OP
super stock
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OP
super stock
Joined: Jan 2009
Posts: 903
Oregon
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I was looking at some 8 3/4 third members today-and I noticed a problem with 2 of them. One of them I remember was a 489 case-and I will try to explain what I noticed. On the opposite side of the ring gear where the big bolts are is a ring which is next to the ring gear teeth which is a couple inches wide. Anyway this ring has teethmarks on it where for some reason it appears the pinion gear must be scarring that ring up. Sorry for my bad explanation-but it looks like to me-the pinion gear is marking/scarring this ring area up. Something must be worn or misadjusted? Also is the 489 case rebuildable-i have heard yes and no
also I have heard that the 489 case is rebuildable-and not rebuildable-which is true
Put a big block 4 speed Scat Pack Dodge in your garage.
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Re: 8 3/4 third member question-what is wrong
[Re: rtplumcrazy1]
#1469598
07/18/13 03:21 AM
07/18/13 03:21 AM
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Joined: Mar 2003
Posts: 4,848
Memphis
HemiRick
master
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master
Joined: Mar 2003
Posts: 4,848
Memphis
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I can only help with the rebuildable part. Yea a 489 case can be rebuilt. The confusion comes from the sure grips. The 489 case had the cone type sure grip which was not meant to be rebuilt, but some people have a way to grind them to give them more life. Unlike the 742 sure grips which used clutches and are meant to be rebuilt.
Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
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Re: 8 3/4 third member question-what is wrong
[Re: Cab_Burge]
#1469601
07/18/13 03:14 PM
07/18/13 03:14 PM
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Joined: Jan 2003
Posts: 26,032
Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 26,032
Rio Linda, CA
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The 489 was also used in the '68 model year.
The INTERNET, the MISinformation superhighway
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It is not uncommon for the 489 crush sleeves to collapse and let the pinion gear slide back into the posi case and leave teeth marks 
BTW, some of the 489 came with the Dana type clutch posi from Mopar, 1969 was a transition year on the 8 3/4 third members, both on the cases and the posi units 