1973 Plymouth Duster repair and rebuild

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I have been in debate over this topic with my neighbor who knows way too much doing his own fabrication. Do you have any good references I can point him to supporting your advice and what I found? I wanted 5 degrees down from level. He provided a compelling argument for why 8 degrees up.
The Mopar Performance suspension manual. That and because I said so. lol We're not talking about working angles of the u-joint here. That's different and dependent on what the angle of the transmission output shaft is. This is the angle of the pinion center line as related to the spring perches. Lots of people confuse the two.
 
The Mopar Performance suspension manual. That and because I said so. lol We're not talking about working angles of the u-joint here. That's different and dependent on what the angle of the transmission output shaft is. This is the angle of the pinion center line as related to the spring perches. Lots of people confuse the two.
Thank you. I believe what your saying is correct as it is similiar with other resources I have read. Unfortunately, the pinion is weled 8 degree's up from reference of perches. And that is incorrect. Well, I will yank the 8.8 from the barracuda which is setup correctly and hide this rear in under that car until I can pull it and do it again.

Do you have any insight on why the measured angle on the barracuda would be 8 degrees pointing up from perches? Other than someone did it wrong and installed it in barracuda to get rid of the evidence? LoL
 
Stock housings position the perches such that the pinion is pointed UP 5* relative to the perches.

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Wait a min, you both are exact opposite +/- 3 degrees. Are the values on my barracuda rear axle near correct? They look factory install. I have not had the rear out of the duster yet as its on wheels keep the car safe to work on the front end. I thought I would be pro-active and get the rear prep'd for installing while I waited. This seems to have been the worst idea ever.
 

Thank you. I believe what your saying is correct as it is similiar with other resources I have read. Unfortunately, the pinion is weled 8 degree's up from reference of perches. And that is incorrect. Well, I will yank the 8.8 from the barracuda which is setup correctly and hide this rear in under that car until I can pull it and do it again.

Do you have any insight on why the measured angle on the barracuda would be 8 degrees pointing up from perches? Other than someone did it wrong and installed it in barracuda to get rid of the evidence? LoL
Well, it MIGHT be correct for "whatever" application it WAS in. Not everything is automatically 5 degrees down. Most older Mopar applications are. Again, you may be confusing pinion angle with U-joint working angle. In other words, have you actually MEASURED the relationship between the spring perches and pinion centerline? You cannot just "climb under" and measure it static on the vehicle, since the spring perches are probably not plumb and level. Understand?
 
Well, it MIGHT be correct for "whatever" application it WAS in. Not everything is automatically 5 degrees down. Most older Mopar applications are. Again, you may be confusing pinion angle with U-joint working angle. In other words, have you actually MEASURED the relationship between the spring perches and pinion centerline? You cannot just "climb under" and measure it static on the vehicle, since the spring perches are probably not plumb and level. Understand?
I can not. My drive way slopes down hill quite a bit. The rear tires have blocks preventing it from rolling down hill while the front end is on Jack Stands under the K Frame and A pillars. I was trying to be pro active. Figured set the pinion angle using my digital angle finder and set the perches to 0 degrees. Then weld. That sounded easy enough. And would minimize the time the rear end is up with less safety issues on the hill. More so, since I am not on flat ground, I dont want the car way up in the air. Up high enough to get the axle in, then get the car back on the ground.
 
Can anyone confirm that the 7.25 is the same between the 1969 barracuda (a-body) and a 1973 duster? I always thought a 7.25 for A-body was the same across all.
 
I can not. My drive way slopes down hill quite a bit. The rear tires have blocks preventing it from rolling down hill while the front end is on Jack Stands under the K Frame and A pillars. I was trying to be pro active. Figured set the pinion angle using my digital angle finder and set the perches. Then weld. That sounded easy enough. And would minimize the time the rear end is up with less safety issues on the hill. More so, since I am not on flat ground, I dont want the car way up in the air. Up high enough to get the axle in, then get the car back on the ground.
Whether the vehicle is on level ground or not hasn't a thing to do with pinion angle or working u-joint angle. You can flip the car upside down and take the measurements and come out with the right figures. That is, IF the suspension would remain in the static loaded position. Sticking an angle finder on the pinion with the rear end installed in the vehicle is not reading the actual pinion angle as related to the perches. That's the point I'm trying to get through.
 
Can anyone confirm that the 7.25 is the same between the 1969 barracuda (a-body) and a 1973 duster? I always thought a 7.25 for A-body was the same across all.
Well of course it's not. One is big bolt pattern the other is small. Other than that, I THINK they're the same. @Charrlie_S can lay it on us if they're not.
 
Whether the vehicle is on level ground or not hasn't a thing to do with pinion angle or working u-joint angle. You can flip the car upside down and take the measurements and come out with the right figures. That is, IF the suspension would remain in the static loaded position. Sticking an angle finder on the pinion with the rear end installed in the vehicle is not reading the actual pinion angle as related to the perches. That's the point I'm trying to get through.
I understand that now. Then the question is, what is the angle in reference to the perches? Could the 8 degrees measured from my barracuda be correct?


Well of course it's not. One is big bolt pattern the other is small. Other than that, I THINK they're the same. @Charrlie_S can lay it on us if they're not.
Yes the obvious is the bolt pattern change. And maybe the brakes, but backing plates can be swapped to match the car installed on.

And maybe given all this, the axle is setup correctly.
 
just spit balling here but is the pinion pointing 'up' in relation to the leaf spring perches because the part of the leaf they bolt to is sloping downwards towards to front? so when the car is at ride height the pinion isn't pointing 'up' at all.
neil.
 
just spit balling here but is the pinion pointing 'up' in relation to the leaf spring perches because the part of the leaf they bolt to is sloping downwards towards to front? so when the car is at ride height the pinion isn't pointing 'up' at all.
neil.

That makes sense.
 
It depends on the Duster brakes at the front. Disc cars are 4.5" bolt circle, and drum on all 4 cars are small bolt to 76.
I should have elaborated as the context of the question was regarding geometry. I am pulling off a small bolt pattern rear on this 1973. I am not concerned about the bolt pattern size as the intent is to goto large bolt pattern ford 8.8. What I was trying to ask, the housing sizes, perch locations, and pinion degree as compared to the perches.

I guess the correct question would have been, could a 1969 barracuda 7.25 rear end bolt on a 1973 small bolt pattern duster? If so, would it work fine, would the drive line geometry correct?
 
I understand that now. Then the question is, what is the angle in reference to the perches? Could the 8 degrees measured from my barracuda be correct?



Yes the obvious is the bolt pattern change. And maybe the brakes, but backing plates can be swapped to match the car installed on.

And maybe given all this, the axle is setup correctly.
No you don't understand. For the third time. The angle in reference to the perches is 5 degrees nose down.
 
No you don't understand. For the third time. The angle in reference to the perches is 5 degrees nose down.
Your right, I dont understand. I am so confused and I am at the point of giving up until I can get a job and pay someone to do this.

And if the barracuda axle geometry is different than the duster axle geometry, then I really screwed up. As my new 8.8 is welded up like the barracuda axle.
 
Your right, I dont understand. I am so confused and I am at the point of giving up until I can get a job and pay someone to do this.

And if the barracuda axle geometry is different than the duster axle geometry, then I really screwed up. As my new 8.8 is welded up like the barracuda axle.
I don't know how else to explain it and I've told you which publication to get. Anyone who owns a Mopar should have the MP engine and suspension books and I don't understand why everyone DIGS IN when I suggest that. It's almost as if people don't want to learn.
 
OMG, I hate this rear seat. I know I am suppose to push down and back, then lift. But it feels like its bolted down preventing it from moving. Yet I can not find anything.
 
Meanwhile, check out this modern solution for Blue Dots. Will get pictures in the evening a bit later. I am just testing now.

Right now the LED is on a dedicated circuit. I will probably give myself some options to tie to the tail light or brake light when its done.

If you look closely, you will see the blue rings around the tail light lenses. I kind of like how it turned out.
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OMG, if only you could see the grin on my face. The effect looks great. The LED on the passenger side is lit so I can show a comparison between driver and passenger.

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Well, I placed a wanted add on craigslist for a mobile welder to complete the suspension brackets. Sit and wait.

If anyone here is in the Pierce/King county WA area, let me know. I even have the welder.
 
So I have not shown any interior shots as of yet. With the down time from working on mechanical aspect of the car, I have spent time cleaning the interior. This car is as clean as this picture makes it out to be. The carpet is toast as is the missing headliner. But the rest is really nice.

I really like the earlier doors with the metal tops inside. And I may look at that change at a later time. Have metal tops made, or swap the doors for the 1972 (ish???). The panels are a bit distorted and curling out at the edges some. But still really clean. If its possible to move the fabric on the panels to new backing, this would be really nice. If I was going to have done this, I would have used blue piping instead of the red.

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The pinion on a stock A body rearend points upward 5* relative to the perches.
You know what? I think you might be right, in which case I humbly apologize.

...and I know exactly where my mix up is. Because I always set them up UPSIDE DOWN on jack stands using a floor jack to position the center section and in that case, it IS nose DOWN...which of course if nose UP once installed. My bad.
 
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