Driveline Angle and Pinion Angle

badazz81z28

Veteran Member
May 4, 2001
22,129
Alabama
Well my new Moser 9" rearend makes noise in 5th and 6th gear. While cruising, steady pedal with no acceleration. Let of the pedal and the noise goes away. Called Moser and they stated its my pinion angle....Sure ok....

So I'm checking my angle relative to the ground and seems about right. Then I start researching and it seems my pinion down angle should be relative to the driveshaft not the ground.

I'm confused, I thought I had this right in my head and now I'm questioning myself.
 

Goat

Veteran Member
Lifetime Gold Member
Jun 7, 2001
1,950
moncure, NC
Yep, all the angles, tranny, rear, 'pinion' are all relative to each other. The ground has nothing to do with the measurements...
 

badazz81z28

Veteran Member
May 4, 2001
22,129
Alabama
That's what I thought. When they say "-2 degrees down" I have been thinking -2 degrees down from being parallel with the driveshaft. That's correct right?

What would people be so concerned about level on the ground? What ground will be 100% flat?
 

badazz81z28

Veteran Member
May 4, 2001
22,129
Alabama
It's so inconsistent it's not even funny
 

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badazz81z28

Veteran Member
May 4, 2001
22,129
Alabama
So spending like 3 hours playing with my pinion angle and this calculator, it seems to wants the opposite of the engine angle. I got to where it was consistent passing results, but the pinion was at an upward angle (I'm guessing 1.5 up while the engine was 1.5 down. Watching videos it seems that's where U-joints are happy.

So educate me here, why would Detroit Speeds specs be -2 degree pinion and -3 for transmission? I'm confused....
 

SRGN

Veteran Member
Feb 20, 2009
681
Central NJ
The pinion needs to angle downwards. Ideally, setting pinion angle will allow the driveshaft and pinion to be straight under load. The pinion will rise upwards under load, and bring the driveshaft with it. Under deceleration with a manual transmission in gear, the pinion will angle downwards. You need to find the right setup for your car which will keep deflection of the joints under 3 degrees under deceleration and around zero while accelerating. This may involve getting excessive torsional movement out of the suspension by replacing bushings, etc. I usually shoot for 2 degrees pinion angle for a street driven car. A drag only car can see between 1 and 3 degrees, adjusted as necessary. Leaf spring cars are a nightmare if you don't know how much the spring "wraps" under load. Traction bars have a duality of purpose on a leaf spring car, since they both apply force to lift the car under load, and limit rotation of the differential housing to prevent pinion angle from going beyond the operational limits of the u joints.
 

Goat

Veteran Member
Lifetime Gold Member
Jun 7, 2001
1,950
moncure, NC
I used to be confused about this too, until I did a lot of research. As SRGN points out, these "ideal" pinion angles you read about are dynamic not static, i.e. "under load". Most people leave out that part because they don't know how to quantify it - very hard for the average person to measure angles while accelerating/cruising. There is a very good post on here somewhere about someone measuring angles with a camera while driving.

With all the high performance, aftermarket parts we put on these Camaros, angles can be all over the place. On my last build before this one, I spent a lot of time playing with different shims to get my pinion angle in a good spot...
 
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badazz81z28

Veteran Member
May 4, 2001
22,129
Alabama
What you think? I guess I can drive it and see what it does. Visually right now it looks straight. But it's hard to eye ball 2degrees
 




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