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Old 12-22-2005, 06:56 AM
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how to determine correct pinion angle

would appreciate some input on determining the correct pinion angle before installing the drive shaft

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Old 12-22-2005, 07:31 AM
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We have covered that fairly extensively..Check some of willys posts and do a search of the data base and you will find a lot on that..

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Old 12-22-2005, 07:58 AM
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Pinion Angles and Driveline Setup for the Street

The information in this post was collected from several different articles on the subject and a number of web sites. Where quotes are used the author is directly credited for his statements.

If you talk to a dozen car guys about pinion angle you?re going to get 12 different opinions. Why? Because optimum pinion angles and settings will vary depending on things such as intended use and suspension type. What works for one suspension type under one condition may not work for another. Sounds confusing doesn?t it. That?s probably why so many people ask for help on this subject. Let?s try to explain some of this mystery.

The guidelines below are specifically recommended for street driven vehicles. Settings for drag racing will differ and are especially dependent on suspension type. For instance a 4 bar rear suspension has much more control over the pinion angle under all operating conditions than a parallel leaf spring suspension does. Therefore pinion angle can be much better controlled with a 4 link and the required pinion angle can be somewhat less than a leaf spring setup. This applies to racing only. When it comes to a street driven vehicle, which is the subject of this post, the recommendations below apply no matter what suspension is used.

First we have to understand what pinion angle is. For our purpose pinion angle is defined as the angle of the pinion in relation to the angle of the drive shaft. This is measured referencing absolute level or for all intense and purposes, the ground. In the example below the angle of the drive shaft is 3* down in relation to level and the pinion is set 1* nose down in relation to level. This makes the effective pinion angle -4*.





The angle of the pinion gear isn?t the only important angle we have to deal with. There are other angles and components at play and they all have to work together to successfully transmit the engine?s power to the axles. The pinion angle?s relationship to the transmission output shaft angle (or crankshaft angle) and driveshaft angle is also extremely important. This relationship defines the angles at which the ?U? joints operate and according to Ray Currie of Currie enterprises, ?universal joints are designed to handle angles between 1 and 3 degrees. If a U-joint is forced beyond this normal range, it can hyperextend and lead to catastrophic failure.? In the example above the ?U? joint would be operating at 4 * or outside its designed parameters. This is why we need to control the relationship between pinion angle, the angle of the drive shaft and the angle of the transmission. Each affects the other.

According to Currie, ?a street driven vehicle should strive for between 1 and 3 degrees between the transmission and driveshaft, and 1 to 3 degrees between the driveshaft and pinion. Furthermore, the two angles should be nearly equal (between 1 and 3 degrees), but always opposite.? Otherwise stated, ideally, the angles between the transmission output shaft and driveshaft, and between the driveshaft and the pinion will be equal and opposite and 3 degrees or less. See the example below.





When setting pinion angle it is important to remember that exceeding the above parameters will result in premature wear of ?U? joints and angle induced vibrations in the drive train. Greg Frick of Inland Empire Driveline explains it this way. ?As the front U-joint gets the power delivered to the driveshaft, it transforms smooth engine power into pulsating power. This happens because the U-joint travels an elliptical path caused by the angle through which it operates. You can visualize this by looking at a dinner plate straight on.





If you tilt it the round plate appears to become an ellipse. In traveling this ellipse, the U-joint speeds up and slows down twice per shaft revolution. A second U-joint having an equal but opposite angle is used to convert this pulsating power back into smooth power feeding the pinion. The bigger the working angles are, the more violent these speed changes become.? Deliberately setting the pinion at a lesser angle is common on drag cars where the drive line is generally under full power however using this type setup on the street will result in annoying vibrations every time you back off the throttle. This is why it is extremely important to limit the angles to 3* or less.

In summary, it isn?t just the pinion angle that?s important. It?s the relationship between the driveshaft, transmission output shaft, and the pinion gear that is important and this relationship governs the angles at which the ?U? joints operate. It?s really not that difficult. All you have to do is keep the pinion angle and the transmission output shaft angles as close to parallel as possible and try to keep both angles at 3* or less. This is relatively easy for a full sized vehicle but the shorter the drive shaft the harder it is to control these angles.

There is also a school of thought that having some pinion angle is not required. Yes a driveline will work with 0 pinion angle however the "U" joints need a slight angle for proper lubrication. Running with 0 angle will prematurely wear out "U" joints.
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