Rear axle Perpendicular to ground!

[ScotM]

Ohhhhhhh

Seems a control arm issue like you sussed it out in an earlier comment.

I’m just wondering what a stock rear axle angle should be?

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[autotragic]

I’m just wondering what a stock rear axle angle should be?

Measure where the pinion comes out of the front of the differential. That's the number that matters not what the back of the differential is doing.

Then ideally you want to measure the yoke at the back of the transfer case to see what the angle of it is. Once you have those numbers get back to us.

 

[jberry187]

I think most people are picturing your Jeep lying on its side.

Exactly this…

 

[ScotM]

Thanks. I’ll check that

 

[SoK66]

Your rear pinion angle should not be 0 degrees, it should be about 1 -2 degrees less than the angle of your driveshaft to allow for rotation under acceleration. So, if you have a driveshaft angle of 11.4 degrees, and your pinion is rotated up about 9.4 degrees you are roughly on the money.

I'm not getting why you swapped out the rear control arms along with the Mopar 2" kit. The kit comes with longer front lower arms. Your angles (caster/pinion in front, pinion in rear) should be right on the money. What am i missing?

 

[Mx5red]

This was a really long thread to just ask, “what should my pinion angle be?”

 

[ScotM]

Your rear pinion angle should not be 0 degrees, it should be about 1 -2 degrees less than the angle of your driveshaft to allow for rotation under acceleration. So, if you have a driveshaft angle of 11.4 degrees, and your pinion is rotated up about 9.4 degrees you are roughly on the money.

I'm not getting why you swapped out the rear control arms along with the Mopar 2" kit. The kit comes with longer front lower arms. Your angles (caster/pinion in front, pinion in rear) should be right on the money. What am i missing?

The front is right on the money for caster snd pinion . I swapped out the rears , that are stock, with better performance parts. I just replicated the sizes of the parts I removed, but since the lift didn’t come anything different for the rest besides longer end links, I assumed the lifting the Jeep with the same fixed rear control arms, would change the angles in the setup. No that I have adjustesble rear control arms, I could bring the geometry back to where it should be. But I’m going to check the pinion angle this afternoon. I appreciate your response ?

 

[Old Jeeper]

I did the mopar 2” lift, and was wondering if the rear axle should be perpendicular to the ground , just as the front is. I installed adjustable control arms, but set them at the same length as the stock, and the angle is about 9.4 degrees negative at the rear. My front is about 0.4 negative. Both measurements being off the differential flat spot at parallel to ground. Going to shop to have it aligned, but just wanted input from the jeppers here. Thanks!!

Parallel to the ground.

 

[RicRecon]

I think most people are picturing your Jeep lying on its side.

I was picturing the axle straight up in the air perpendicular to the ground and thought “nope, I’m not responding until others do on this one.”

 

[ScotM]

Measured the pinion angle at 4.5, so that’s out of spec. Also noticed a ridiculous number of weights welded to the driveshaft. Great manufacturing.

 

[DLW]

Pinion angle is 4.5 compared to what, the ground?
If you get the pinion at -2 from whatever the driveshaft is, then you should be good to go, as was mentioned earlier.

 

[ScotM]

Pinion angle is 4.5 compared to what, the ground?
If you get the pinion at -2 from whatever the driveshaft is, then you should be good to go, as was mentioned earlier.

Driveshaft angle as related to pinion gear

 

[ScotM]

Driveshaft angle as related to pinion gear

did it 2 ways. First, angle of axle at flat spot on differential back - near the cover, there are two reference points, see previous picture with blue highlighted area

as baseline angle, then angle of drive shaft. Difference in angles about 4.5 degrees. Second. Baseline angle fron flat spot on bottom of differential, which should also match pinion gear angle inside hosing, then measured driveshaft angle. Same resulting difference of about 4.5 degrees. I think I’m doing it correctly, and visually there is definitely an angle more than 1 degree

 

[JLfromCA]

The axels relationship to the ground is only controlled by the tires. The body/frame relationship to the ground would be controlled by the springs.

 

[ScotM]

The axels relationship to the ground is only controlled by the tires. The body/frame relationship to the ground would be controlled by the springs.

I’m obviouly not making myself clear here. The differential and axle can be shifted with the control arm length.

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