Re: Pinion angle help
[Re: 383BeepBeep]
#1598414
03/25/14 10:07 PM
03/25/14 10:07 PM
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Joined: Jan 2003
Posts: 6,591
Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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Quote:
There is way to much information on pinion angle out there, that I am confused. I bought an angle finder and took measurements. The confusion comes in when doing the math. If the pinion is facing down does that angle get a + or a -? So I drew a picture. Could someone please dumb down the whole pinion angle equation? Thanks
I'll try. In your drawing you are 6.5* nose down from parallel.
The easiest thing to do from your drawing is to rotate the tranny angle up to 0 to parallel from your 2* down. For explanation sake.
Its now easy to see that your pinion angle is now 4.5 nose down from parallel.
But your tranny angle is down 2* down, so being down 2* your pinion angle is 6.5* down. At 0 it would be 4.5* down. If the tranny was 2* up you would have a 2.5* down pinion angle.
Your driveshaft angle only comes into play if its to extreme, meaning if the axel is Much lower then the tranny centerline.
Correct pinion angle is so the U-Joints work together well both under power and on decell.
I am sure, this is still not clear to many, it never is. 
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Re: Pinion angle help
[Re: 383BeepBeep]
#1598416
03/25/14 10:25 PM
03/25/14 10:25 PM
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Joined: Jul 2008
Posts: 240
Plano, Texas
68cuda440
enthusiast
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enthusiast
Joined: Jul 2008
Posts: 240
Plano, Texas
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Quote:
There is way to much information on pinion angle out there, that I am confused. I bought an angle finder and took measurements. The confusion comes in when doing the math. If the pinion is facing down does that angle get a + or a -? So I drew a picture. Could someone please dumb down the whole pinion angle equation? Thanks
If I am interpreting correctly your diff is pointing 4.5 degrees downward toward the u-joint. You sum that angle and the driveshaft angle (assuming your drawing representation on the driveshaft sloping down to the rear).
Looks like you are 8 degrees nose down at the rear joint and 1.5 at the front. Since the slope of the driveshaft and transmission are the same direction you subtract.
Per the Mopar Chassis Manual, 9th Ed. Chapter 6.
Front U-joint should be 2.5 degrees or less, but not zero.
Rear U-joint
Standard Leaf: 5-10 degrees nose down, 5-7 preferred
Leaf Link: 3-5 degrees nose down
4-Bar (double pivot) link: 2 degrees nose down
Ladder (single pivot) link: 1 degree nose down
Oval Track Leaf Spring: 4-5 degrees nose down
So, in other words, if you have a leaf car you should be OK, but you could be better if you took 1-2 degrees out of the diff. If you do not have vibration cruising or under deceleration, then you are likely OK where you are.
-Michael
Michael
1968 Barracuda Notchback Coupe
440 EFI 6-pack, T56 Magnum 6-spd
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Re: Pinion angle help
[Re: 383BeepBeep]
#1598418
03/25/14 11:13 PM
03/25/14 11:13 PM
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Joined: Jan 2003
Posts: 6,591
Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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BEEP, Since you can draw on the pute.  Can you Fix your drawing to show the different angles between the diff and the tranny. Alls you have now is a Single angle shown between the tranny and diff that really doesnt show anything but that angle. If you can, Show a flat horizontal angle. Then add in your Trannies 2* down and your Diffs 4.5* down angles in relationship to that. I can do this,  Horizontal _________________________________ As per your info, you are 6.5* nose down as is..
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Re: Pinion angle help
[Re: 68cuda440]
#1598419
03/26/14 12:33 AM
03/26/14 12:33 AM
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Joined: Jan 2003
Posts: 6,591
Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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Quote:
Quote:
If I am interpreting correctly your diff is pointing 4.5 degrees downward toward the u-joint.
Thats a wrong interpretation, The diff is pointing down 4.5 degrees from parallel measured by a angle finder thats based off of a parallel plane.
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Re: Pinion angle help
[Re: 383BeepBeep]
#1598420
03/26/14 12:48 AM
03/26/14 12:48 AM
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Joined: Jan 2007
Posts: 780
Woodinville, WA
Viol8r
super stock
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super stock
Joined: Jan 2007
Posts: 780
Woodinville, WA
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Quote:
There is way to much information on pinion angle out there, that I am confused. I bought an angle finder and took measurements. The confusion comes in when doing the math. If the pinion is facing down does that angle get a + or a -? So I drew a picture. Could someone please dumb down the whole pinion angle equation? Thanks
It comes down to working angles. The front working angle (1.5º) is in the ballpark. The rear is almost (8º) assuming your I am reading the drawing correctly. You want to try to keep it at or under 3º of working angle. Most likely need to get some different shims for the leafs.
Example: take your 4.5º of pinion and go to 1º to 1½º. That to me should look better.
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Re: Pinion angle help
[Re: Sport440]
#1598421
03/27/14 12:12 AM
03/27/14 12:12 AM
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Joined: Jul 2008
Posts: 240
Plano, Texas
68cuda440
enthusiast
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enthusiast
Joined: Jul 2008
Posts: 240
Plano, Texas
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Quote:
Quote:
Quote:
If I am interpreting correctly your diff is pointing 4.5 degrees downward toward the u-joint.
Thats a wrong interpretation, The diff is pointing down 4.5 degrees from parallel measured by a angle finder thats based off of a parallel plane.
What I mean is the nose is lower than the axle tube, correct? Parallel to the ground correct?
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Re: Pinion angle help
[Re: Sport440]
#1598424
04/17/14 03:20 PM
04/17/14 03:20 PM
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Joined: Apr 2011
Posts: 1,520
West Palm Beach, Florida
Copper Dart
pro stock
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pro stock
Joined: Apr 2011
Posts: 1,520
West Palm Beach, Florida
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Just my o-pinion (pun intended)
I just dealt with this same issue on my build. I found that once I got it (middle drawing) into my head, it was very easy to understand.
Study and understand the middle picture. It clearly shows a 0.0* relationship pinion to transmission.
What I found confusing was that I kept seeing transmission as a Horizontal line. Forget Horizontal, its just the "drawn" engine/transmission center line.
If you lift the rear of your car by the rear axle/wheels till the engine/transmission are level, then it makes it easier to understand pinion down/up (IMO).
Common sense, the least common of all the senses.
Mom.
For fear of ridicule, society stifles creativity.
Ricky Valdes
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,though not much help 
