Pinion angle help.

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va-mopar

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I'm a tempting to set pinion angle on my 70 Duster. Any help/ advice would be greatly appreciated. It was a 318 with 904 trans and 7 1/4 rear. I put in a 360 and a 8 3/4 rear. It still has 904 tranny. I just took angle off tailshaft and it is. 1 degree down. What should the pinion angle be. The rear end don't have perches , so I will be weilding them on after I set the correct angle. Thanks in advance.
 
Is the one degree down relative to the drive shaft?
 
If the transmission is 1 degree down you want the pinion .5 or 1.5 down. Try for .5 degrees delta between the two
 
Cuda69. I don't understand. Relative to drive shaft? Currently there's no drive shaft in.
 
Cuda69. I don't understand. Relative to drive shaft? Currently there's no drive shaft in.


Good question!!! You're supposed to get your pinion angle set relative to your transmission angle (engine drive line). If you read all the web sites I posted you'll know what to do. You don't even need a drive shaft.

Treblig
 
I'm a tempting to set pinion angle on my 70 Duster. Any help/ advice would be greatly appreciated. It was a 318 with 904 trans and 7 1/4 rear. I put in a 360 and a 8 3/4 rear. It still has 904 tranny. I just took angle off tailshaft and it is. 1 degree down. What should the pinion angle be. The rear end don't have perches , so I will be weilding them on after I set the correct angle. Thanks in advance.

If the pinion is 1 degree up, they would be parallel. Are you using any traction devices to control spring wrap? Ideally, you want the pinion a certain number of degrees lower than 1 degree up to allow for the nose of the pinion to climb upward a bit under power, and then be parallel to the transmission centerline.

The number of degrees of adjustment downward on your case depends on which type of limiter you use to control the rotation of the pinion upward under power. If you are not using a traction device, then you probably want 2 or 3 degrees nose down at rest to allow for the upward rotation under power. If you use a traction device to limit that movement, it can be as little as .5 degree lower.
 
If the pinion is 1 degree up, they would be parallel. Are you using any traction devices to control spring wrap? Ideally, you want the pinion a certain number of degrees lower than 1 degree up to allow for the nose of the pinion to climb upward a bit under power, and then be parallel to the transmission centerline.

The number of degrees of adjustment downward on your case depends on which type of limiter you use to control the rotation of the pinion upward under power. If you are not using a traction device, then you probably want 2 or 3 degrees nose down at rest to allow for the upward rotation under power. If you use a traction device to limit that movement, it can be as little as .5 degree lower.
Transmission tail shaft is 1 degree down. Not up. I don't currently have any traction devices.
 
Transmission tail shaft is 1 degree down. Not up. I don't currently have any traction devices.


Then your pinion should 1 degree up when the rear end in under a load (acceleration), which is usually around 2 degrees down in the static position. Under normal circumstances the pinion will rise about 3 degrees when you stomp on it depending on your rear suspension (leaf, 4 link, traction bars). But keep in mind that the static pinion angle (2 degrees down) is based on standard leaf spring car. If you limit the upward rotation of the pinion with traction bars then the angle changes. In the end if the pinion angle is parallel to the engine drive line when the rear end in under a load it should be OK>

treblig
 
Transmission tail shaft is 1 degree down. Not up. I don't currently have any traction devices.

I understand. The pinion is located in the rearend.

Keep in mind, you are checking the angle at the back of the transmission and at the front of the rear end.

It helps me to visualize it by drawing a circle and then draw one color line at the angle of the transmission/engine and then draw another color line through the circle at the angle of the pinion in the rear end. The lines should intersect at the center of the circle.

The pinion line will rotate clockwise 1 to 5 degrees under acceleration depending on your rear suspension, traction devices, no traction devices and power input. You can consider the trans centerline fixed.
 
Good question!!! You're supposed to get your pinion angle set relative to your transmission angle (engine drive line). If you read all the web sites I posted you'll know what to do. You don't even need a drive shaft.

Treblig[/QUO
thanks Treblig
 
Then your pinion should 1 degree up when the rear end in under a load (acceleration), which is usually around 2 degrees down in the static position. Under normal circumstances the pinion will rise about 3 degrees when you stomp on it depending on your rear suspension (leaf, 4 link, traction bars). But keep in mind that the static pinion angle (2 degrees down) is based on standard leaf spring car. If you limit the upward rotation of the pinion with traction bars then the angle changes. In the end if the pinion angle is parallel to the engine drive line when the rear end in under a load it should be OK>

treblig
Thanks' It is a leaf spring car. I'll set the pinion angle at 2 degrees down.
 
thanks Treblig

You're welcome, after you get it set and start driving the car here's how you check to make sure you have it correct. They make (Summit/Jegs) angle shims to make minor corrections to the pinion angle:


Checking to see if you have got it correct:
If there is no vibration under normal operating conditions then the angles are correct.
If there is vibration under acceleration, you need to add more downward pinion angle preload. If the opposite occurs, the vibrations tends to decrease or disappear under acceleration, you need to reduce the downward angle preload.

If the vibration steadily increases with driveshaft speed (either accelerating or decelerating) the symptom is primarily the result of a driveshaft imbalance or yoke runout. Sometimes this yoke runout problem can be improved by rotating the U-joint 180-degrees in the rear end differential yoke.

Driveshaft-related vibrations usually occur at roughly engine speed in high gear. Wheel/axle vibrations usually occur at 1/3 rd engine speed or driveshaft speed because of the differential gearing. To determining whether it is the output of the transmission or the pinion in the differential, change gears when the noise occurs and maintain speed. If the vibration/noise changes in frequency, the source is in the transmission or engine. If the frequency remains the same it is a driveline problem.

Good Luck
Treblig
 
Last edited:
You're welcome, after you get it set and start driving the car here's how you check to make sure you have it correct. They make (Summit/Jegs) angle shims to make minor corrections to the pinion angle:


Checking to see if you have got it correct:
If there is no vibration under normal operating conditions then the angles are correct.
If there is vibration under acceleration, you need to add more downward pinion angle preload. If the opposite occurs, the vibrations tends to decrease or disappear under acceleration, you need to reduce the downward angle preload.

If the vibration steadily increases with driveshaft speed (either accelerating or decelerating) the symptom is primarily the result of a driveshaft imbalance or yoke runout. Sometimes this yoke runout problem can be improved by rotating the U-joint 180-degrees in the rear end differential yoke.

Driveshaft-related vibrations usually occur at roughly engine speed in high gear. Wheel/axle vibrations usually occur at 1/3 rd engine speed or driveshaft speed because of the differential gearing. To determining whether it is the output of the transmission or the pinion in the differential, change gears when the noise occurs and maintain speed. If the vibration/noise changes in frequency, the source is in the transmission or engine. If the frequency remains the same it is a driveline problem.

Good Luck
Treblig
Thanks Treblig. I will keep that in mind.
 
I see this posted all the time. A stock A-body Mopar is in the PDF I attached.
 

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  • MOPAR PINION ANGLE.pdf
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Pinion angle is dependent on eng/trans angle. If your car is totally factory stock 5 degrees down may be the exact thing that you need but after 60 years and many previous owners/modifications 5 degrees may not work. If you get your trans angle and set the pinion angle accordingly then you should be OK!!

Treblig
 
It's best to mock it up. Your perches actually will be sitting on an arc.

But I see people confused about what direction the pinion angle is at in regards to even starting.

If you put 5 degrees the wrong way, it quickly turns into 12-14 degrees the wrong way.
 
Be sure to measure the pinion angle with the rear suspension loaded.....
u want it to be near perfectly in line under hard load. will be dependant on how hard u load it,and traction devices to control it.
 
update.. I put rear in car front wheels sitting on ramps and rear sitting on spring perches U bolted (tight but enough to move) with tires on and sitting on blocks. Car level and all weight on wheels , and set pinion angle at 3 *. And I put a 2x4 between the tire and leaf spring on both sides (thinking that would square up the rear). Unfortunately, after finishing up everything I test drove car and There is a noise on exceleration at any speed. I pulled third member took it and had it re-setup, put it back in and test drove again and noise on exceleration. Totally frustrated, I put car on lift and measured left to right between leaf spring and backing plate and found that the driver side and passenger side are not even. Would this cause the Noise ? Or is the pinion angle still off or both? The third member has all new parts and only aprox. less than 20 miles on everything. all thoughts and comments on this welcome.
 
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