8 3/4 rear end

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Joe334

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Hi guys, im getting ready to buy an 8 3/4 rear end from a salvage yard and i am planning on getting a new ring and pinion for it, but what i need to know is what case number is this rear end? Does it have the number on the pumpking or somewhere around it? I was looking in summit and it has a 489 and a 742 as my choices for the case number. Or does the casenumber not even matter? The rear-end is out of an old dart, 1969 i believe. Anyone know what case number went with this car? What ratio would be good to stick in this thing? I am building it to be a street/strip.
Thanks,
Joe
 
Joe334 said:
Hi guys, im getting ready to buy an 8 3/4 rear end from a salvage yard and i am planning on getting a new ring and pinion for it, but what i need to know is what case number is this rear end? Does it have the number on the pumpking or somewhere around it? I was looking in summit and it has a 489 and a 742 as my choices for the case number. Or does the casenumber not even matter? The rear-end is out of an old dart, 1969 i believe. Anyone know what case number went with this car? What ratio would be good to stick in this thing? I am building it to be a street/strip.
Thanks,
Joe
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Either or! I don't think it'll mater which one your put in, either a 489 or a 742. Just stay away from the 741 case if you plan on putting any real power in fron of it. I think a 489 is more desirable, but you won't break either one of them. As for a gear, there are too many variables involved with choosing a gear ratio. I think a 3.91 would be a great choice if you want to wake your car up and don't plan on too many long trips on the freeway.

Oh yeah, the number of the carrier is the last 3 digits of the casting number on the side of the pumpkin.
 
You`ll find that there are more gear ratios available for the 489 case (than any of the others) which is probably what it is, if it was original to the 69 Dart. The 741 (early 60`s) has a small pinion gear, followed by a larger 1.75 straight pinion in the 742 (late 60`s)and a 1.825 tapered pinion in the 489. The 489 case first appeared in mass on`69 cars. Like mopowers said, check the left front of the pumpkin for a casting#. The last 3 will designate what case it is.
 
It could easily be a 741, I have seen 741's in lots of a bodys as mopar was trying to get ride of them they put them in the lighter cars. A little tid bit on the 741, even though we as mopar guys think the 741 is undesirable the pinion is about the same size as a 12 bolt GM car pinion which GM guys think is indestructable.
 
I had a 741 case in my car for 5 years of beatings. Never had a problem with it. &41s are a little harder to find gears for though.
 
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