hey guys i have a 8 1/4 rear end sitting around i want to put it on my 74 duster the guy that i bought it from say i need new brakes for it does anyone know what size drums i need also what type of gear oil i need and how much also do i need a different drive shaft i have the drive shaft for the rear end too it came from a 318 with a 904 trans will this work with my 904 or can i use the one that is already on my car this will be my first rear swap so i don't know what i need

Whats the 8 1/4 out of?
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

You need to figure out if the rear end has 10" brakes (very likely) or 11" brakes (rare for an A-body) and then you can order brake parts for just about anything form '73-'76 with that size brakes.

If it's a regular open differential (one axle spins forward and the other backward) any good 80W-90 GL-5 gear oil is fine. If it's got Sure-Grip you'll want the limited slip additive so the clutches don't chatter.

If you have the driveshaft from the same car as the rear end that's good as long as the donor car was the same wheelbase as your car. Your car is 108" wheelbase so you need a 49.9" long driveshaft.

I just swapped the 7 1/4 in my 108" wheelbase Valiant for an 8 1/4. I hope you got the U-bolts and plates that mount under the leaf springs. U-bolts can be had new no problem, but the plates under the springs are harder to come by.

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Joshua

the rear end is out of a 73 dart i have the bottom plate so i don't have to worry about that but i am going to need new u bolts and it is not a sure grip the guy had one but he was not selling it

OK, so you'll need a driveshaft too. You can have yours shortened or try and find the proper length.

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Joshua

yeah i have two different drive shaft when i bought the rear end also is the rear end going to have a different bolt patten for the tires i will let you guys know how it go i will be doing it over the weekend

hey guys i was wondering since the gears will be different will this hurt my mpg at all

Do you know what your current ratio is, and what ratio the 8 1/4" has installed?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

i know that the 8 1/4 is 2.71 and the 7 1/4 rear end is 2.76 that is what the tags says on them what is the best way to tell if i have a sure-grip

how much gear oil do i need for the rear end

4.4 pts of GL-5

-D.Idiot

ok good to know so today i got it mostly off just the e-brakes and the main brake line

There won't be enuf of a difference between a 2.71 and a 2.76 to even notice.

so i am also done with the rear i have brake lines to do and get a drive shaft so my question is what car will work for a drive shaft??

1973-1976 Plymouth Duster w/8.25" rear
1973-1976 Dodge Dart Sport w/8.25" rear
and any Valiant with the 108" wheelbase (2 door non hardtops)
with the 8.25" rearend...

Or put your yoke into the tranny, with about 3/4" of tube out of the tailshaft, measure bewteen the center of the eye on the yoke and the center of the eye on the axle (where the u-joint caps would be), and have one made at a drivleine shop/ have your old one cut down...

-D.Idiot