Street A bodies with springs moved into the rails

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Sedanman

Sedanman

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My car had the springs moved into the rails (front) but work halted and I bought the car. The front boxes are flush with the outter frame rail and stick out on the inside. If yours is set up the same way what is your axle width drum to drum and what is the perch to perch measurement? I just picked up a narrowed 8 3/4 that is 54 1/4 wide out of a Chevy Vega and need to figure out if this width is ok before I start hacking the Vega brackets off.
 
Sedanman said:
My car had the springs moved into the rails (front) but work halted and I bought the car. The front boxes are flush with the outter frame rail and stick out on the inside. If yours is set up the same way what is your axle width drum to drum and what is the perch to perch measurement? I just picked up a narrowed 8 3/4 that is 54 1/4 wide out of a Chevy Vega and need to figure out if this width is ok before I start hacking the Vega brackets off.
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mopar_axle_sizes.jpg
 
I know what stock is. I need the measurements for cars with the springs moved into the frames
 
Sedanman said:
I know what stock is. I need the measurements for cars with the springs moved into the frames
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I believe he was trying to say that your going to have to measure your actual spring width when they're installed to get your perch measurement .
 
To get the center to Center spring perch measurement, how come you can't measure the center to center of your frame rails, or more accurately the center to Center of the spring boxes that were welded in?
 
Because the axle I just bought is with me and my car is in storage 30 miles away. I was hoping someone had a similar set up
 
Valiant63 said:
To get the center to Center spring perch measurement, how come you can't measure the center to center of your frame rails, or more accurately the center to Center of the spring boxes that were welded in?
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You just solved the riddle

Get under there with a tape measure and MEASURE
 
It looks like I typed that just as he posted the fact about his car being in storage
 
If it helps, I believe rear framerails are 36" center to center.
 
It is not a riddle. Every customization is different.
The relocation is done. Bolt the springs in the front and see where they land under undue pressure.
Adjust the axle spring perches accordingly. Be sure to include the pinion angle. The shackle is a little forgiving and may need more frequent maintenance.
 
I'm pretty sure you're going to be at 35 inches Center to Center, that's assuming that your new front spring mounts extend an inch from the frame rail on each side.
 
Valiant63 said:
I'm pretty sure you're going to be at 35 inches Center to Center, that's assuming that your new front spring mounts extend an inch from the frame rail on each side.
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He said the outside of the spring box is flush with the frame.
Regardless of what everyone says it should be, don't jump the shark. Wait until you measure it on YOUR car for real before you start cutting and welding anything. I learned along time ago, every car IS different. Measure for yourself. TWICE. Also measure from your frame to the quarter panel lip. Measure for square also. You don't know who welded those boxes in. Take your time, make sure it is right. You have the chance to center your rear diff in there now, take that opportunity.
 
Bodyperson said:
View attachment 1714990852
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RustyRatRod said:
I think that's the chart that's WAY not right. @crackedback can tell us if it is.
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That chart is hideous. I can tell you right now it's not right, because it lists the 7.25" and 8 3/4" as being the same width. Not even close. Heck the 8 3/4" width isn't even right. The perch to perch measurement is about the only thing on that chart that is right (43" for A-bodies). Where the heck do these things come from? Who measured that crap? Blind carpenters? :realcrazy:

Um, if the car in question has had the springs relocated to the frame rails that should be the 3" relocation, so, the perches should need to be about 37" c-c. Now, the frame rails are wider than the springs so that's not perfect, the car MUST be measured before the perches are installed. But that's the ballpark. And bodystyle doesn't matter, all A-body frame rails are the same width.

The width at 54 1/4" needs to be more specific. If it's the flange to flange measurement it's a little wider than an A-body 8 3/4, if it's drum to drum (mounting surface to mounting surface) it's a few inches narrower. It's more than close enough to make something work, just depends on how much you want to play with the backspacing.

A-body 8 3/4 flange to flange : '66-'72= 52 5/8” (BBP 7.25/8.25 = 51.5”)
drum to drum: 66-'72= 57 1/8” (or 57 13/16” for BBP axles and brakes)

And if you're curious
A-body BBP 7.25/8.25 flange to flange= 51.5”
drum to drum 8.25/7.25 = 56 3/4”
 
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Thanks. I thought that was the one that was wrong.
 
Have we answered the OP question? I was trying to let op know the width of an a body axle housing.
This is an A body discussion forum.
 
Bodyperson said:
Have we answered the OP question? I was trying to let op know the width of an a body axle housing.
This is an A body discussion forum.
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I thought I did in #18. At least as best I can at the moment.

The 8 3/4 he has should work, but it's not the same width as an A-body 8 3/4. Not sure if the measurement he gave is flange-to-flange or drum-to-drum. His 8 3/4 is either a couple inches wider or a couple inches narrower than a stock A-body 8 3/4, either way it's close enough to be compensated for.
 
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