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Old 05-14-2005, 08:46 PM
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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.

Hope this has taken some of the mystery out of setting up your driveline.

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Old 05-15-2005, 05:54 AM
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I'm afraid the preceding post perpetuates the popular misconception that there MUST be a driveline angle when using U-joints. Nothing could be further from the truth! The 3 degrees cited is a LIMIT, not something to be desired. When a driveline angle is unavoidable, the arrangement should be as pictured, for the speed variations at the two U-joints then tend to cancel (assuming the two U-joints are oriented properly). But, with a change in number of passengers or load in the trunk, there will always be an additional angle variation. It is far more desirable to have that variation occur about a perfectly aligned (straight) driveline than about one which is deliberately offset by 3 degrees. In other words, the variation is going to cause a problem in any event, so you might as well start with the minimum wear/vibration condition.
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Old 05-15-2005, 11:31 AM
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Quote:
Originally Posted by BillyShope
I'm afraid the preceding post perpetuates the popular misconception that there MUST be a driveline angle when using U-joints. Nothing could be further from the truth! The 3 degrees cited is a LIMIT, not something to be desired. When a driveline angle is unavoidable, the arrangement should be as pictured, for the speed variations at the two U-joints then tend to cancel (assuming the two U-joints are oriented properly). But, with a change in number of passengers or load in the trunk, there will always be an additional angle variation. It is far more desirable to have that variation occur about a perfectly aligned (straight) driveline than about one which is deliberately offset by 3 degrees. In other words, the variation is going to cause a problem in any event, so you might as well start with the minimum wear/vibration condition.
I have no argument with your assertion, however there are very few if ANY vehicles that have the "perfect" zero angle driveline setup you mentioned, with the possible exception of some IRS setups. If you know of any others I would be interested to here what they are.

Although the zero angle setup might seem optimum, it's not all that practical. When weight is added to the vehicle, providing the suspension is designed correctly, there is little or no change in the relationship of the angles between the two "U" joints. In my post above as weight is added the relationship actually moves toward a zero angle rather than away as it would if it was set up with a zero to begin with. This is a much more desirable condition for a street driven car since they carry extra weight from time to time. With a zero angle driveline you only have 3* of movement before you are at the recommended limits when weight is added. With the setup described in my post (as recommended by Currie and other driveline professionals) you have up to 6* of movement as weight is added before reaching the recommended limits. I agree that you have little movement before reaching the recommended limits if weight is removed but this would be a very rare condition.

Basically the closer to zero your initial setup is the fewer degrees of movement you have (when weight is added or under acceleration) before you reach the recommended limits. As the rear end squats under hard acceleration the angles will move again as if weight has been applied to the rear end. If you start with zero and have a couple buddies in the car and then stomp on it, you could easily exceed the 3* recommended limit.

No argument that zero is the "optimum" but reality is another thing altogether.

Last edited by Centerline; 05-15-2005 at 12:10 PM.
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Old 05-15-2005, 01:01 PM
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Yes, I agree that you must design for average load and maximize usable U-joint angle, but, as my first sentence clearly stated, there is a popular misconception that a drivetrain angle is both necessary and desirable and it is that misconception which I was addressing. For maximum U-joint life and minimization of vibration problems, it is desirable that the drivetrain be "straight" with an average load. I recognize that, having said that, a manufacturer might choose to sacrifice some of the U-joint life to accomodate an occasional overloading which might otherwise result in a sudden failure. But, if the builder of a street rod realizes that he's never going to be moving a load of bricks in his trunk, he might wisely choose a different starting angle.
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Old 05-15-2005, 01:59 PM
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Point well taken.
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Old 05-15-2005, 04:21 PM
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I have always set up the motor & trans mounts with the carb set level. In a SBC the engine/trans will be pointed down 3 degree from horizontal. I then set the pinion angle 3 degrees up. comments?

Don
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Old 05-15-2005, 06:12 PM
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To find out what your effective angle is you need to measure the angle of the drive shaft. If the drive shaft is at 3* then you have a zero pinion angle. If the drive shaft is at 6* then it would be 3* etc. The shorter the drive shaft the larger the angle is likely to be and the more effect it will have on your pinion angle.

In the graphic below the first example is a fairly short wheel base car that is set up as you described. In this case due to the angle of the drive shaft it has an effective pinion angle of 5* which would be outside the recommended limits



In the second example, a slightly longer wheel base vehicle (with the same effective ride height), the drive shaft angle is a few degrees less which changes the effective pinion angle to 2* which is inside the recommended limits. I admit that both of these are just examples but you can see that just setting the pinion at the same angle (reversed) as the trans isn't the only angle that has to go into the equation.
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Old 05-16-2005, 08:54 AM
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Bill, (Centerline) your last diagram hit my tilt meter. I think you should forget level with the ground to get the concept right; ie, think of the drive unit working in the vertical. The key issue is to get the extended centerline of the tranny output shaft parallel to the extended centerline of the pinion shaft. Ideally for every day driving this would be under 3 degrees. Just look at some of the extreme angles of the short drive shafts in raised and lifted 4WD mudders and you can see some angles that stretch the operating limit of the U Joints. (Borgenson joints for steering setups are limited to about 20 degrees, but this is apples and oranges) I am sure there are some mudders out there operating with close to 10 degrees drive shaft angles with respect ot tranny/pinion shaft centerlines. And, yes, there are some slight vibes involved, often masked by the big, aggressive tires.

Trees
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Old 07-08-2005, 05:57 PM
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Whether you use the ground as a reference or the trans output shaft, the theory is exactly the same. The two charts above simply show how driveshaft length effects the driveshaft angle all other angles being equal. If you check the other examples I've posted you'll find the (dotted line) is an extension of the trans output shaft and does not represent the ground.
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Old 07-29-2005, 11:52 PM
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Straight driveline no good.

The standard ujoint is designed to "pump grease" as it turns. sort of pressurizing the bearings. The movement required is gained by a 1-3 deg angle. if straight, it will still oscillate, but not enough for proper lubrication, so straight is as bad as too much angle. (If by straight you mean straight line thru tranny, drive shaft and pinion of rear end)
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Old 05-03-2007, 08:03 PM
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where are the diagrams?

i am trying to set up my coupe..using a 34 ford coupe frame mounting a lincoln 460/c6/9". as i understand what i am reading.As looking down from above it all..the centerline of the tranny/driveshaft and pinion is aligned. This puts the motor off to the right (passenger)side of the car about 2" inside the frame rails.As looking from the side, tranny down 1-3, pinion up same as whatever the tranny is and also limited to 1-3 and but going up(equal but opposite), with the drive shaft connecting the two. Also i dont see any of the diagrams as mentioned above...where are they?...and am i right with the setup figures?
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Old 05-03-2007, 08:28 PM
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Here are the images. Don't know why their not showing up in the original post.

Wrong:


Correct:


Ellipse example:


Example in my second post:


You're understanding is correct. The information I posted did not come from my brain. It came from three or four articles written by some experts in the field.
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Old 05-03-2007, 08:31 PM
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There is no mystery to drive line set-up! The mystery occurs when confusing and sometimes incorrect advice is given on forums like this. The best source of information is from companies who's business is drivelines. Inland Empire Driveline in Calif. has a brochure free for the asking on driveline set-up. These people are experts on driveline angle. They have on many occasions provided seminars at NSRA events on just this subject. Denny's driveline is another source as well and has information available on his website. If you had chest pains would you talk to your neighbor or a Doctor. Get expert advice, and it doesn't cost you anymore money.
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Old 05-03-2007, 08:49 PM
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A few things to add.
I like to compare the eliptical pattern of each of the u joint travel patterns to that of a rear differential going around a turn meaning that the outside wheel turns faster but they both end up at the same speed at the end of a turn. So imagine a pair of u-joints accross each other on the crossshaft, they both go thru the rotation , but one has to travel furthur on the outer angle and speeds up to keep up with the inner angle u-joint and in the mean time the other two cups on the same joint are doing the same thing but in a differant rotation pattern just 90 degrees off. And once it makes a full revolution the cups switch travel and the one that travels faster now takes the slower route to go thru one rotation.
The importance of this is the action of the u-joints speedup and slowing down causes the driveshaft to speed up and slow down thru the rotation. The more the driveline angle the more the shaft occilates. This is the big reason to having the front a rear u-joint working angles to match is so the occilation of the driveshaft is the same thru out the whole driveshaft.
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Old 05-03-2007, 09:03 PM
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I agree with the above, both sides!

I also want to remind everyone thet they need to align the driveshaft left and right also.
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