I have a friend telling me he can get me a decent deal on a used 8 3/4" rear axle for the Dart with the 489 casting.

I originally wasn't planning on changing out the rear axle to match the (upcoming) front discs bolt pattern since I planned on putting 15x12" mags on the rear anyway, but I figure if this has the 4.5" bolt pattern, it couldn't hurt (can never have too much strength I figure) to just go ahead and do it. Can anyone tell me if all 8 3/4" axles have the same bolt pattern, and if so, what it is?

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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

A-body 8 3/4's are all 5 on 4". Every other 8 3/4 is 5 on 4 1/2".

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

Does it absolutely have to be an A-body 8 3/4, or can I use non A-body 8 3/4's as well?

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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

Supposedly, there are some particular b-body 8 3/4's, which are only 2" wider spring pad to spring pad. 'They' say you can spread the leaf spring 1" per side and horse them in. I am not going to recommend doing that because I bought a Duster from a repo yard that somebody had done that, and the rear frame rails were cracked in the area of the rear shackles. But maybe that was one that was more than 2" wider. If you cutoff the spring pads and rewelded them in the proper location, that should be OK.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

Bud's right. I too have seen someone spread the springs to bolt the rear in. Don't do this. The rear that is close is the '66-'70 B-body 8 3/4. Have someone cut the spring pads off with a plasma cutter. This puts less heat on the housing which reduces warping. If you do use a torch go slow and don't cut close to the tube, finish the last bit by grinding. New spring pads are not much money so don't try to reuse the old pads, it will make the job harder. They only need to be moved an inch or so. One side at a time can be done so the other pad can be used for a level reference (to keep the stock pinion angle). Axle flange measurement on the B-body housing is more than 1" per side but A-body wheels use different backspacing so the overall ends up about an inch.

Cecil

Where can I get new spring pads? I live close to a welding/machine shop so relocating the pads on a B-body is easily do-able.

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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 had a '71 Dart that had a '69 Roadrunner rear under it when I bought it. The pads were not moved and the springs did not need to be spread much. The difference in the width of the spring pads was minimal. You will need some wheels with a lot of backspacing to get them under the fenders though.

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Official Cookie and Mater Tormentor.

I have installed a few of these B-Body 8 3/4 into A-Bodies, I never liked the idea of spreading the leaf springs so here is what I have done.

I bought a new set of spring pads ($16/set from Mancini Racing or Just Suspension) then I took one and cut it in 1/2 with my friend's fancy band saw. Made a perfect cut, right through the center locating hole. Now I have two extension pieces

Now just fit the new 1/2 pad inboard of the current spring pad and weld it on. You will need to do some "fit-up" trimming and it is best to grind or pilot drill-out the side wall of the current pad, right where the othe half of the new locating hole will be. ( the 1/2 pad's half center hole will show you where the other 1/2 of the hole needs to go)

You will also have to drill two large holes through the old pads, to allow the outboard "U" bolts to pass through them. (The shock plate can be used as the template to locate those holes.)

Basically, you use half of the current pad and just weld an extension onto the inner side of it. The nice thing about this method is that it is real easy to locate the extension's position, right off the current pad's flat surface. The job can be done "at home" in about an hour. (if you have an arc welder, grinder and a HD drill motor.) If you do not have a welder, get everything layed-out & ready, then take it to a local welder, it's about 15 minutes of welding if you take you time.
DD

The last time I messed with new spring pads ( it's been 15 years) I noticed the centering hole in the new pad was larger than the stock pad. I just pushed the housing forward to the front edge of the hole and tightened the U-bolts. Are the new pads still like this? If so, is there new centering bolts available with a larger head that fit tighter in the pads locating hole?

Cecil

Was the axle itself much wider, or are the spring pads the only thing I have to worry about?

I'm trying to figure out how much backspacing I'm going to need on the wheels I order if I get a B-body axle.

I assume the A-body 8 3/4 axle is the same width as the smaller, stock A-body axle?

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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

Yep, the A-body 8 3/4 is the same width as the A-body 7 1/4 axle, but the plates that the u-bolts go through are larger (larger u-bolts, also).

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'68 Dodge Dart 4dr Sedan

'62-'70 B-body is listed as 44" on the spring pads and a track width of 59.2". '66-'74 A-body is listed as 43" on the spring pads and 55.6" track width. B-body is 1" wider on the spring pads and 3-1/2" wider overall.

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Official Cookie and Mater Tormentor.

Sweet, so an extra 1.25" of backspacing on the wheels and I'm good to go. Woohoo!

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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

You would actually need 1.75" more backspacing. I recommend you look at 90s Mustang wheels, which mostly have 5.72" backspace and could work in that application.

Lou

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Home of Slant6-powered fun machines since 1988

WOOPS, yeah, math flub there, heh

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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