1974 Dart Sport 489 Differential Question

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Warren

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Hello, my Hang 10 purchased used came with the dealer sticker and originally was a 318 with a 3.23 axle ratio. It now has a 360 and a 8.75 489 differential case. According to my factory manual, 1974 Darts did not have the 8.75 available so my question is:

Is my 8.75 489 case a retrofit or were there some 1974's supplied with the 8.75 489 from the factory?

Thanks.
 
74 318 should have been 8.25..does the 8.75 have large bolt pattern?? I'd bet it was from earlier year? I have a 74 with 1970 8.75 but it still has small bolt pattern.
 
74 318 should have been 8.25

Yes...^^^^^....Never seen a 74' A body with a 8.75. And a ratio in that range would have been a 3.21 with a 8.25. It would be interesting though if it was by chance a dealer installed rear? Just be glad you have what you have.....You're $$$ ahead of the game. :thumbrig:
 
No A Body after 72 ever had a factory installed 8 3/4 this was also the same year they got rid of Small Bolt Pattern. (except some 73 Slant 6 Stripper cars which had 4 wheel drums)
So If it is Big Bolt Pattern the axels were swaped or drilled out

1974 with a slant 6 or 318 would have been a 7 1/4 or 8 1/4 from the factory
8 1/4 being an added cost option
 
Thanks everyone for the info. Yes the axles are the big bolt pattern as have the original Rallye wheels with largeacorn center caps. I did find a receipt where the axle stud plates were welded up and re-drilled by Moser in 1993 so I assume the axles are not original. I have a lot of receipts of this car but no info on the differential other than a 4.10 ratio gears installed in 2000. I have since replaced that with a 2.94 for better economy and hiway cruising.
 
If the small bolt pattern axles were re drilled then they would have had to re drill the brake drums also. The A-body 8 3/4 small bolt rear used a axle offset specific to this rear end. Are the drums drilled also?
 
Also, NO A-body 8 3/4" ever came with anything other than the small bolt pattern!
 
Sgbarracuda:
I am not sure the brake drums were drilled (or just replaced) but my memory says there is a 5 hole drilled spacer plate between the drum and axle (I would have to remove a wheel to confirm).
 
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