A-Body Shackle Angle

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SSing

SSing

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Hi,
I´m about to take measurements for a new drive shaft. Body is in the rotisseries, and I can´t put any load on rear axle. Will the rear spring eye move 4” to the rear, to put the shackle in correct angle, when car is build and on the ground? Leaf springs are SS 002-3
I don’t mind put ½” spacers with the front hangers, since this will give me an additional ½” for tire clearance. Car is ´68 Barracuda.
What if I build the driveshaft to original spec. which is 44.8” in this application, but decide I need the spacers, and have to pull the drive shaft out ½”, will this affect the strengths of the spline engagement with the slip yoke in transmission?

I have tried to explain this to the best of my ability, and hope for your experienced advice.
Thank You
Stefan
20160625_161838[1]ShackleAngle.jpg
 
The answer is yes they will move back. Several guys have had the cars up with the shocks off and had the shackles lock over center forward of the mount. You have to make an effort lowering the car to make sure the springs don't do this. Situation normal. The front spring arch is what affects spline and yoke relationship. There are several threads on driveshaft length that you can review and get a comfortable number from. If you are running the seal with the dust boot on the tail shaft then you need to be careful about making the shaft too long. What transmission are you running? The 1/2" should be a non issue if your shaft is in spec.
 
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I wouldn't measure for a driveshaft until the car is on the ground, loaded.
 
The new front spring segment I doubt will change axle position too much over/under stock length, should it?.
 
mguner said:
The answer is yes they will move back. Several guys have had the cars up with the shocks off and had the shackles lock over center forward of the mount. You have to make an effort lowering the car to make sure the springs don't do this. Situation normal. The front spring arch is what affects spline and yoke relationship. There are several threads on driveshaft length that you can review and get a comfortable number from. If you are running the seal with the dust boot on the tail shaft then you need to be careful about making the shaft too long. What transmission are you running? The 1/2" should be a non issue if your shaft is in spec.
Click to expand...


Thanks All. What You say make sense. Except for mguner´s remark about the front arch effecting the spline and yoke relationship. You may be right, but I don´t understand how... Front segment on SS-springs are stiffer than stiff... and mine are gonna bee even stiffer, if possible, with clamps...
It´s a 4-speed.
Like You say I build the drive shaft when car is on te ground, since I believe the angle of the shackles is important, on order for the springs to work well at take off...
 
mguner said:
The answer is yes they will move back. Several guys have had the cars up with the shocks off and had the shackles lock over center forward of the mount. You have to make an effort lowering the car to make sure the springs don't do this. Situation normal. The front spring arch is what affects spline and yoke relationship. There are several threads on driveshaft length that you can review and get a comfortable number from. If you are running the seal with the dust boot on the tail shaft then you need to be careful about making the shaft too long. What transmission are you running? The 1/2" should be a non issue if your shaft is in spec.
Click to expand...


And also like you say, 1/2" less is no issue. That is what I think too... Thanks.
 
If you don't need more room for tires and are worried about shackle angle, space your rear hanger forward and you won't have to mess with the driveshaft length.
 
To clarify about front spring arch. The relationship I was referring to and thought you were too is the depth and in out travel of the yoke in the transmission. Since SS springs have very little wrap in front, the distance from rear axle to transmission changes very little so the yoke moves in and out very little. The other factor is change in body lift and the axle swing which again is minimal when you consider the thickness of the chord of 4" of travel on a 2' radius.
 
pozest said:
If you don't need more room for tires and are worried about shackle angle, space your rear hanger forward and you won't have to mess with the driveshaft length.
Click to expand...

Yes you are right about that, but I hope to be able to run 29" at least...
 
mguner said:
To clarify about front spring arch. The relationship I was referring to and thought you were too is the depth and in out travel of the yoke in the transmission. Since SS springs have very little wrap in front, the distance from rear axle to transmission changes very little so the yoke moves in and out very little. The other factor is change in body lift and the axle swing which again is minimal when you consider the thickness of the chord of 4" of travel on a 2' radius.
Click to expand...

Yes, right now i follow you... Thanks
 
I did a little more research in the subject, and found this. This of cause will put the leaf spring forward. 1/4 of an inch to be exact. I doubt the Ramchargers Guys made these offset brackets other than the production car brackets, when it comes to this measurement. On the other hand one never knew with those guys :)

Well may be we have someone here on the board reading this, and can tell if the original SS-cars had the front offset hanger spring eye on the same distance from the frame , as the production cars front hangers.
It´s more likely though, the kids that set up the tool today, don´t pay enough attention...
20160625_200122[1]HangerComparation.jpg
 
Crackedback is right about measuring with weight on the axle. If everything is else is in the factory location a factory length shaft should be fine. I moved the rear end back 1/2" on my Dart and ran a factory length shaft with no problems.

As far as the rear end moving back and forth in reality it's very little if any unless the front segment wraps up. As the spring (rear segments) load and flatten out it makes the rear half longer and moves the shackle back.
 
justinp61 said:
Crackedback is right about measuring with weight on the axle. If everything is else is in the factory location a factory length shaft should be fine. I moved the rear end back 1/2" on my Dart and ran a factory length shaft with no problems.

As far as the rear end moving back and forth in reality it's very little if any unless the front segment wraps up. As the spring (rear segments) load and flatten out it makes the rear half longer and moves the shackle back.
Click to expand...

Ok thanks Justin,
I have a Dana 60, and it would be interesting to know the difference if any, between the 8 3/4 and the Dana 60 if you measure axle centerline to pinion yoke j-unit centerline?
When I refer to the 44.8" drive shaft, is a figure I got from the SS Hemi Guide of Jim Schild. In it, it says the four-speed Barracudas should have this 44.8" shaft, but this is about 4" to short, which make me think I need the 48.6" Drive Shaft also mention, but used with the Dart´s. This doesn´t make sense, since these bodies are different in wheel base.
Any way I need a 48.6" some Drive Shaft...
 
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