Correct way to set rear angle?

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rod7515

rod7515

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Ive read all posts on setting the rear angle. I guess its time to weld my saddles tight and I want to make sure I have used the correct method to setting my angle. I know where I took the pictures I am a little on the strong side and have since moved it to be at 6* instead of 8*to 9* as it shows in my pics. But was wondering if this is a correct method for setting this.
I put my angle protractor on the front balancer and find the center line is at a strong 4* degrees. Then I put the protractor on the rear housing and also on the pinion yoke and have a negative 4* to 5* degrees. This means I have approx 8* to 9* degrees down? I have since moved the rear to be at about 2* to 1* down which should put me around 6* down which is where I think I want to be. Also I do have the weight sitting on the rear tires so the axle is not hanging. I also plan on adding supports on the back and front of saddles for extra strength. I just want to make sure this is correct before I weld!
Thanks
Rod

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rod7515 said:
Ive read all posts on setting the rear angle. I guess its time to weld my saddles tight and I want to make sure I have used the correct method to setting my angle. I know where I took the pictures I am a little on the strong side and have since moved it to be at 6* instead of 8*to 9* as it shows in my pics. But was wondering if this is a correct method for setting this.
I put my angle protractor on the front balancer and find the center line is at a strong 4* degrees. Then I put the protractor on the rear housing and also on the pinion yoke and have a negative 4* to 5* degrees. This means I have approx 8* to 9* degrees down? I have since moved the rear to be at about 2* to 1* down which should put me around 6* down which is where I think I want to be. Also I do have the weight sitting on the rear tires so the axle is not hanging. I also plan on adding supports on the back and front of saddles for extra strength. I just want to make sure this is correct before I weld!
Thanks
Rod

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interested, getting ready to check mine. looks like it`s ok to me !
 
Treblig, Thats the exact article I used to set up my thought pattern. It shows that the rear must run parallel to the transmission output shaft which is just an extended line from the center of the crankshaft. Using the balancer as a 90* reference and the face of the rear housing on a 90* reference I am thinking that I had the parallel lines. Then by dropping the rear down 6-8* should give me the 6-8* drop? I am asking if my thought pattern is correct. I just dont want to weld and find out I miss understood. So are you saying yes its good?
Rod
 
Not trying to be rude, but how do you expect to get a correct pinion angle without checking driveshaft angle? I must be missing something.

When I did mine on both cars, leaf springs on first and ladder bars on this one, I followed the procedures in the second area titled G. Driveshaft Angle that is included in what Treblig posted above, which came out of the MOPAR Chassis Book.
 
rod7515 said:
Treblig, Thats the exact article I used to set up my thought pattern. It shows that the rear must run parallel to the transmission output shaft which is just an extended line from the center of the crankshaft. Using the balancer as a 90* reference and the face of the rear housing on a 90* reference I am thinking that I had the parallel lines. Then by dropping the rear down 6-8* should give me the 6-8* drop? I am asking if my thought pattern is correct. I just dont want to weld and find out I miss understood. So are you saying yes its good?
Rod
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Well they say that for the least amount of drive line vibration your rear center line should be parallel to the engine/trans center line. But it really isn't clear about "when" they should be parallel. That being said, depending on your rear end suspension (ladder bars, springs, etc) the amount of differential rotation (they all rotate up) will determine the corrective angle "down" because the pinion will rise under acceleration. So (now I'm thinking out loud), if your pinion rises 2 degrees (example) you should position it 2 degrees lower that the place where it would be if it were parallel. This way, under load, the pinion will rise into a position which will be parallel with the engine drive line diminishing vibrations and increasing the life of the drive line components. Remember that old leaf springs are softer and allow more pinion "vertical movement", also the number of spring "stabilizer" clamps will stiffen the springs and increase spring rigidity.
Can anyone else AGREE or DISAGREE???

Worst case scenario, If you're off by a degree or two after welding you can easily slide and angle shim in there and correct/perfect the angle.

treblig
 
What suspension are you running and do you plan on driving this on the street a lot?

Looks like a leaf, SS spring?

If driving on the street try to go no more than 3-4* down. Any more than that and the U-joints get a real beating.
Track only, 6* down would be OK.

Street driven car, I'd limit the pinion to level or 1* up.
 
crackedback said:
What suspension are you running and do you plan on driving this on the street a lot?

Looks like a leaf, SS spring?

If driving on the street try to go no more than 3-4* down. Any more than that and the U-joints get a real beating.
Track only, 6* down would be OK.

Street driven car, I'd limit the pinion to level or 1* up.
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Do you mean 3-4 degrees down from parallel?? It gets confusing if you're not real specific. In the end doesn't it depend on how much his pinion rises under load?

Treblig
 
I have new SS springs that have just been in installed. I plan on racing this car 3 -4 times a year. I will also be driving this on the street but not that often. My engine builder who also races has suggested 6* no less. I think I am there but dont want to weld if I am wrong? Thanks for all the suggestions.
Rod
 
"driveshaft angle" is misunderstood. It really should be called "output shaft angle" which is the same as crank centerline. if the crank is tail down 6 and the diff is nose up 6, you are at 0: with the tendency for the diff nose to rise up under torque, you want it to be down in its natural state and the angle is dependent on the type of rear suspension you are using so when you are on it, the difference approaches 0 again. Lay rear in unwelded saddles and exagerated nose down state. cinch snug the U bolts. Get car back to road height and sit in it. have mate jack up nose with floor jack to desired level (it will rotate in saddles) let say -4 in relation to crank (output shaft) angle. scribe marks on saddles and tubes or tack weld, then remove and finish saddle weld beads. I found the crank line usually is down a few degrees so the nose is just shy of being level. A zero deflection at cruise is not recommended either as it wears out the U-joints as there is no load across the stationary roller bearings.
 
Still not sure if I am where I should be in order to have a 6-8* drop after reading pishta's explaination. I think I am where I need to be. I set the protractor on balancer and had a positive 4-5*. I then set the rear at the same positive 4-5*. Then I rotated the rear housing an additional 6-8* down. Shouldnt this be the correct setting?
Thanks
Rod
 
rod7515 said:
Still not sure if I am where I should be in order to have a 6-8* drop after reading pishta's explaination. I think I am where I need to be. I set the protractor on balancer and had a positive 4-5*. I then set the rear at the same positive 4-5*. Then I rotated the rear housing an additional 6-8* down. Shouldnt this be the correct setting?
Thanks
Rod
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I think members hesitate to say that your opinion angle is perfect or good because there are factors that other members don't know, like how soft are your springs or how much does your pinion rise under load. I put my pinion angle at 3 to 4 degrees below parallel. This gives the pinion 3 to 4 degrees to rise in order for it to be aligned with the trans/engine. The web site I posted for you also talks about how you determine if your pinion angle is good. After you get it all welded and done you drive down the road, accelerate, decelerate a few times and see where/if you get a vibration. If you notice something during the accel/decel test you simply stick an angle shim in there. This is exactly what I did. It's almost impossible to know how much your pinion will rise unless you attach a GoPro to the underside of your car and hit the road. Sounds like yours is close to where it should be but personally I shoot for 3-4 degrees below parallel. I used to worry about this problem but now I just get it as close as possible to 4 degrees below parallel and shim it if need be. I have a pair of 2 degree shims under my springs right now and I have no vibrations!!!

Treblig
 
rod7515 said:
I put my angle protractor on the front balancer and find the center line is at a strong 4* degrees. Then I put the protractor on the rear housing and also on the pinion yoke and have a negative 4* to 5* degrees. This means I have approx 8* to 9* degrees down? I have since moved the rear to be at about 2* to 1* down which should put me around 6* down which is where I think I want to be.
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This is spot on from a pinion angle approach. You have a -6* angle with the pinion pointing 2* down, trans tail pointing down 4*.
 
OK, sounds like I can weld into place! This was such a tough thing to understand at first because so many people describe this differently. Looking forward to getting this done and moving onto the next step of getting this thing on the road.
Thanks
Rod
 
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