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  #31 (permalink)  
Old 11-02-2011, 10:20 PM
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Quote:
Originally Posted by RatPin
How will raising the car increase the angle of your trans output shaft? Unless you only raise the front.That's what I was addressing.
As far as rear pinion angle goes. On a parralel 4-link there are many factors to take into consideration, but if your bars are less than 36", there will be a change on a 6" stroke like you might find with a bagged setup.
And of course if your bars of of uneven length the angle is going to change throughout the travel of the rearend. But if set up at ride height it is all you can do and all you need realistically.

Brian

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  #32 (permalink)  
Old 11-03-2011, 04:28 AM
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Quote:
Originally Posted by Centerline
I guess I'll have to take the time to educate you on this subject. Whether or not you listen is another story. After all you can lead a horse to water but you can't make him drink.

Driveline basics:

Drive shafts in rear wheel drive vehicles have "U" joints at each end that transfer the rotational energy from the output shaft of the transmission to the driveshaft and then from the driveshaft to the differential. All "U" joints rotate in an elliptical motion, unless the operating angle is exactly zero which is almost never the case. So, this means the "U" joint at the front of the driveshaft and the one at the rear both speed up and slow down twice per rotation. That's why they need to be installed "in phase". Each "U" joint must speed up and slow down at exactly the same time as the other. If they are not in phase vibration is inevitable.

Not only do "U" joints rotate elliptically, the ellipse changes as the angle of rotation changes. In order to keep from creating undue vibration the "U" joint angle at each end of the driveshaft needs to match the other as close as possible so the ellipse the "U" joints travel in are the same. In other words, the angle of the output shaft of the transmission and the differential pinion gear input shaft need to be in the same plane. This helps keep the rotational angles for both "U" joints equal. Differences here will create driveline vibration because as the rotational angle of the "U" joint changes the elliptical path changes and when one "U" joint travels in a different ellipse than the other, vibration is created. Also, the greater the operating angle of the "U" joint, the more distorted the ellipse becomes and the greater the torsional vibration. This is why most "U" joint manufacturers recommend an operating angle of 3 degrees or less. Operating the "U" joint at greater angles is possible but it will cause premature "U" joint failure and driveline vibration due to excess torsional stress.

In summary, for a street driven vehicle the transmission output shaft and pinion input shaft need to be in the same plane, (or parallel) and the angles need to be kept at 3 degrees or less for optimal longevity. Lower operating angles also minimize driveline vibration introduced by the elliptical rotational pattern of the "U" joints. Drag racing and specialized rear suspensions will require different settings but the "U" joints will still operate under the same laws of motion.

Consider yourself educated. Proper driveline angles, when it comes to "U" joints and driveshafts, are critical to effectively transmitting torque and power from the trans to the differential without creating vibration.

Centerline
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I take what you say but why does a car with a jacked up rear,in some cases 12" not affect the driveability or cause viration?
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  #33 (permalink)  
Old 11-03-2011, 05:14 AM
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Quote:
Originally Posted by RatPin
How will raising the car increase the angle of your trans output shaft? Unless you only raise the front.That's what I was addressing.
As far as rear pinion angle goes. On a parralel 4-link there are many factors to take into consideration, but if your bars are less than 36", there will be a change on a 6" stroke like you might find with a bagged setup.
Oh, OK I understand your question... raising the car will not change the angle of the output shaft, but it will change the angle of the driveshaft (since the driveshaft must drop more to meet the pinion). So the angle between the trans output shaft and the driveshaft will increase as the car is raised.

My point was that the trans and pinion angles will not change, but their angles with the driveshaft will become larger as the car is raised - which is not good for the universal joints.
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Old 11-03-2011, 06:03 AM
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If you asked 10 tyipcal street rodders how to set up a pinion angle, only two would get it right. The reason.........because so much mis-information is put out as fact on forums such as this. Instead, try going to a reliable source for info such as just about any GM rear drive, shop manual, a custom drive line shop, or others in the business of drivelines. Inland Empire Driveline has been supplying custom length drive lines for many years, here's what they say about pinion angle:

http://www.iedls.com/Education-Zone.asp?CID=3

Do a Google search for drivelines and get your info from those in the business and not from a thread such as this one which is full of misinformation.

Jim
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  #35 (permalink)  
Old 11-03-2011, 09:18 AM
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If you ask ten typical HOT rodders, I bet 8 would get it right.....
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Old 11-03-2011, 11:36 AM
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Quote:
Originally Posted by user151
My point was that the trans and pinion angles will not change, but their angles with the driveshaft will become larger as the car is raised - which is not good for the universal joints.
Will the U joints be USED when the car is Raised? If you are raising it permanetly then you set the pinion angle accordingly. If you are raising the car with a jack to change the tire, I recommend letting the jack down before driving it and using the U joints.

Brian
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Old 11-03-2011, 12:00 PM
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Quote:
Originally Posted by 5 CWT
I take what you say but why does a car with a jacked up rear,in some cases 12" not affect the driveability or cause viration?
By increasing the ride height the "U" joint angles are increased. If the trans output shaft and the pinion angle remain in the same plane (basically parallel) the natural harmonics of the ellipses are still canceled out. The difference is in the stress put on the "U" joint when operating at a more drastic angle. "U" joints can operate at pretty drastic angles and you can even increase the angle by doing some judicious grinding but.... the greater the operating angle, the shorter the life of the "U" joint. Most jacked up 4x4 guys are very aware of this. The important thing in any setup is to adjust the angles to cancel the ellipse harmonics as best as possible. Different suspensions will require different pinion angles based on how the suspension moves. Also drag racing setups will be different than street setups. Its not rocket science but a clear understanding of what happens between the trans output shaft and the pinion gear when initially setting up a driveline will save a lot of time and experimentation.

Centerline
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Old 11-03-2011, 12:27 PM
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Until I read Centerline's last post I was going to be surprised we even made it this far without refering to harmonic cancelation and phasing ha ha ha ha ha ....

In the 60's 70's those cars that were jacked up in the *** end.. nobody is saying they were right. Also as your (typically) then built car having a set of ladder bars under them would have somewhat kept the driveline angle relatively right depending on the variable. Notice I said relatively... Those cars were also typically sporting 60 series tires that rode oh so nice where you couldnt pick up a driveline vibration...

4x4 guys... it is a complete compromise and anyone with a lifted truck invariably accepts accelerated U joint wear... as far as vibration... Tires usually larger then 35 will omit any notable driveline vibration.
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Old 11-03-2011, 02:36 PM
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Quote:
Originally Posted by Tony@AirRideTech
Until I read Centerline's last post I was going to be surprised we even made it this far without refering to harmonic cancelation and phasing ha ha ha ha ha ....

In the 60's 70's those cars that were jacked up in the *** end.. nobody is saying they were right. Also as your (typically) then built car having a set of ladder bars under them would have somewhat kept the driveline angle relatively right depending on the variable. Notice I said relatively... Those cars were also typically sporting 60 series tires that rode oh so nice where you couldnt pick up a driveline vibration...

4x4 guys... it is a complete compromise and anyone with a lifted truck invariably accepts accelerated U joint wear... as far as vibration... Tires usually larger then 35 will omit any notable driveline vibration.
60 series, N50s baby, N50s. I have a Ford truck at the shop right now with some HUGE tread mud tires my God they shake the fillings out of your teeth going down the street. I don't think he is noticing any vibration from the drive shaft.

Brian
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  #40 (permalink)  
Old 11-03-2011, 04:49 PM
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Too anal for me now guys! I have a honours degree in motorsport engineering and a distinction in technical engineering. I have proved my point. End of my posts in this subject.....
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Old 11-03-2011, 05:28 PM
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Quote:
Originally Posted by user151
My point was that the trans and pinion angles will not change, but their angles with the driveshaft will become larger as the car is raised - which is not good for the universal joints.
Got it. So you weren't actually even talking about pinion. You were talking U-joint angle. The OP was asking about pinion angle, but I see what you mean.
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  #42 (permalink)  
Old 11-03-2011, 05:58 PM
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Quote:
Originally Posted by RatPin
Got it. So you weren't actually even talking about pinion. You were talking U-joint angle. The OP was asking about pinion angle, but I see what you mean.
Yes, I think this thread (myself included) got somewhat astray from the original question, as you pointed out.
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Old 11-03-2011, 06:56 PM
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Quote:
Originally Posted by user151
Yes, I think this thread (myself included) got somewhat astray from the original question, as you pointed out.
Not really that far astray. "U" joint angle and pinion angle are related and how you set the pinion angle has a direct effect on "U" joint operating angles. IMHO, you can't really talk about one without the other.

Centerline
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Old 11-03-2011, 07:06 PM
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I really don't understand why it's so hard to understand how to set the pinion angle..

This is what this thread is starting to look like and case y'all don't know it by now..



I really think he dead by now !!!!!!
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  #45 (permalink)  
Old 11-03-2011, 07:42 PM
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I think the thread is valuable, it is explained many times so almost anyone can understand. I think it's of value to anybody searching the forum for pinion angle information.

Brian
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