Checking pinion angle on jack stands?

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my5thmopar

my5thmopar

Life Long MOPAR Owner
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I can't get under the D100 because its too low to the ground. I'm getting varying descriptions of the process. If jack stands are placed under the axle tubes, and the front tires on cribbing, will the readings be accurate? I know you want to replicate the suspension being loaded. Is this acceptable or do I need to have the rear tires on cribbing too? I know I'm overthinking this but, I want to get the most accurate reading I can. I have to pull the axles again to find out why the new inner seal is leaking. Craig
 
So long as it's LEVEL and sitting as if it's "on the tires" you are good. Basically, under load, the transmission/ crankshaft centerline needs to be parallel with the pinion shaft centerline
 
I was just dealing with this, but on my hoist. Rear axle was on my air jack. I was having difficulty wrapping my head around the angles, so levelled the engine/trans centerline. then i adjusted the diff angle. Got it where i needed it.
used tremec app on my phone.
 
67Dart273 said:
So long as it's LEVEL and sitting as if it's "on the tires" you are good. Basically, under load, the transmission/ crankshaft centerline needs to be parallel with the pinion shaft centerline
Click to expand...

Does level really matter ?
Pinion angle is the difference between the angle of the trany vs driveshaft and angle of the pinion vs driveshaft.
So if your driveshaft angle = X
And trany angle = Y
And pinion = Z

The equation is (X-Y) - (X-Z) = required (Pinion) angle.

So it really doesnt matter what the atitude of the car is because all measurements will be relative .

Is my logic in error?
 
mbaird said:
Does level really matter ?
Pinion angle is the difference between the angle of the trany vs driveshaft and angle of the pinion vs driveshaft.
So if your driveshaft angle = X
And trany angle = Y
And pinion = Z

The equation is (X-Y) - (X-Z) = required (Pinion) angle.

So it really doesnt matter what the atitude of the car is because all measurements will be relative .

Is my logic in error?
Click to expand...

Level matters if you don't want to do some extra figuring.
 
More importantly, if it's not the same attitude as when it's on the wheels, the rear axle may be above or below where it would be in the ground and then your angles are off.

So... Make sure the rear axle is bearing weight and the front is high enough to approximate how it sits on the ground.
 
mbaird said:
Does level really matter ?
Pinion angle is the difference between the angle of the trany vs driveshaft and angle of the pinion vs driveshaft.
So if your driveshaft angle = X
And trany angle = Y
And pinion = Z

The equation is (X-Y) - (X-Z) = required (Pinion) angle.

So it really doesnt matter what the atitude of the car is because all measurements will be relative .

Is my logic in error?
Click to expand...

No it doesn't have to be PERFECTLY level, but you don't want it dangerously off especially on jack stands. Your math, AND THE DRIVESHAFT is not necessarily needed. The pinion angle needs to be parallel under power, to the crank/ trans center line. PERIOD

All you need do is establish the crank angle if it's not level, and the pinion angle and compare the two, and "figure" (guess) how much the pinion will rise under power

The only caveat to leaving the shaft out is you don't want zero between the U joints. They should have "some" angle. Unless you have chopped/ lowered/ channeled the body/ chassis whatever, that should be pretty much OK
 
I was always told on an A body that pinion angle on a stock height car should be 5° down from center level. The pinion will climb under acceleration and under load. This information doesnt really help you with a D100 pickup though.
 
1. Make the pinion parallel to the transmission as a base line.
2. Point the pinion downward 2 degrees from the base line. This is your (street) pinion angle.
3. The vehicle does not need to be level.
 
Stock pinion angle is 2 degrees negative (pinion is pointing downward 2 degrees relative to the transmission). Keep in mind, the transmission is not parallel to the ground.
 
Thanks for all the suggestions. I rechecked it tonight because I was second guessing my initial setup. I'm at about 2.2-2.3 negative and I'm not moving it. My welder decided to act up. I have to work on it or buy a new one to finish the job. I do have a stick welder but, it hasn't been out of the cabinet in years. I'm pretty proficient with the MIG.
 
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