Mopar 8 3/4

1965ply · Oct 2, 2020

I have a 8 3/4 center section it does not have any numbers on case. the gear is a 3:91 non sure grip came out of a 64 pick up, would it be the same as a 742 case?

Fran Blacker · Oct 2, 2020

Some pictures would help.

rumblefish360 · Oct 2, 2020

‘64? I don’t think. That’s the same as the 742 case but closer to the 741 case. There’s 3 other numbers I cannot remember right now but there as weak as the 741.

POMONAMISSEL · Oct 2, 2020

yes pics , please . can't do it without seeing it .

Cranky · Oct 2, 2020

rumblefish360 said:
‘64? I don’t think. That’s the same as the 742 case but closer to the 741 case. There’s 3 other numbers I cannot remember right now but there as weak as the 741.

Weak? How many pinion shafts have you broke on any of them?

RemCharger · Oct 2, 2020

Cranky said:
Weak? How many pinion shafts have you broke on any of them?

Yep might be listening to the wrong grandpas.

john-9 · Oct 3, 2020

1965ply said:
I have a 8 3/4 center section it does not have any numbers on case. the gear is a 3:91 non sure grip came out of a 64 pick up, would it be the same as a 742 case?

the case should have a number on the left side ( if you are facing the yoke ) 1820657 ( used from 1957-64 ) which is the same as the later 741 case or number 1634985 ( used from 1957-64 )which is the same as the later 742 case --- if no numbers at all pull the pinion out 1-3/8 pinion diameter (657 or 741 ) --- 1-3/4 diameter 985 or 742 case -- and yes the myth about the 741 case being weak is just that a myth ,,, in a street car you are good -- you will shear ring gear teeth first or break a carrier cap before the pinion shaft breaks.

rumblefish360 · Oct 3, 2020

Cranky said:
Weak? How many pinion shafts have you broke on any of them?

According to the books...
the desirable case numbers are ....
the not so desirable case numbers are ....

2, is your questions answer.

Mark Barnes · Oct 3, 2020

1965ply said:
I have a 8 3/4 center section it does not have any numbers on case. the gear is a 3:91 non sure grip came out of a 64 pick up, would it be the same as a 742 case?

You should send it to me for verification...

Cranky · Oct 3, 2020

rumblefish360 said:
According to the books...
the desirable case numbers are ....
the not so desirable case numbers are ....

2, is your questions answer.

I know what the books etc say and that's been going on for nearly 50 years. Shaved teeth is common but breaking the pinion shaft isn't. Maybe it's the fault of pinion deflection but if that were the case (no pun intended

), why aren't all the other rears having the same issues? Read this article....and it's not the only one that's been published over the years. http://www.doctordiff.com/blog/tech-info/rearend-pinion-comparison/

Cranky · Oct 3, 2020

1965ply said:
I have a 8 3/4 center section it does not have any numbers on case. the gear is a 3:91 non sure grip came out of a 64 pick up, would it be the same as a 742 case?

Is the case pretty dirty? I've found them when they looked like there were no numbers but upon a good cleaning, it showed up.

rolling_Thunder · Oct 3, 2020

rumblefish360 said:
‘64? I don’t think. That’s the same as the 742 case but closer to the 741 case. There’s 3 other numbers I cannot remember right now but there as weak as the 741.

Are you referring to the 657, 983, and 985 cases? the 657 is basically a '741' case and the 985 is a '742' case... being the 1 3/8" and 1 3/4" pinion diameters

I haven't found definitive info on the 983 case... I know they exist as I have seen them - but never have found out their pinion diameter... they '489' tapered pinon did not exist before it's introduction so I assume the 983 is either a 1 3/8" or 1 3/4" pinion --- anyone know for sure?

MoparLeo · Oct 3, 2020

http://www.waywardgarage.com/tech/rearaxlemopar.html

Mopar 8 3/4

1965ply

Well-Known Member

Fran Blacker

FBBO Gold Member

rumblefish360

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POMONAMISSEL

FBBO Gold Member

Cranky

Banned Henchman #27

RemCharger

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john-9

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rumblefish360

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Mark Barnes

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Cranky

Banned Henchman #27

Cranky

Banned Henchman #27

rolling_Thunder

Well-Known Member

MoparLeo

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