Rear axle Perpendicular to ground!

[Mx5red]

I am trying to be helpful… but three pages in and there still seems to be some confusion about this. You are talking about pinion angle, but keep asking about the angle of your diff in relation to the ground.
It doesn’t matter what the angle on your diff is. It matters what it is in relation to your driveshaft, ie pinion angle. That is what matters, to line up the driveshaft and eliminate vibration. This will vary a little depending on each build/lift.

So take the advice in this thread, research adjusting pinion angle.

here is one of the first links I googled.

https://www.jlwranglerforums.com/forum/threads/rzeppa-joints-and-rear-pinion-angle.39604/post-884262

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[blessidsoul12]

the diff-axle are a non-adjustable relationship. So OP I believe is trying to ask in very simple terms for someone, even someone who doesn't understand pinion angle, to just do this simple task and report back. As we do with our kids sometimes it is easier to just ask them to do something wvennif they don't undersrand the why part.

 

[Remorseless]

Your pinion angle is what it is due to the fact that the Mopar lift only comes with front LCAs and provides no rear control arms to adjust pinion angle. Because when you lift your Jeep you move the axle away from the frame in an arc (axle connected to the frame via control arms, if those arms stay the same length but the distance between the axle and frame increases, the resulting travel is in an arc), with the lift you've pushed the axle past the center point in the arc and now the diff faces downward slightly. This is normal when lifting but keeping stock rear control arms.

If you want to change it you need to get adjustable/fixed control arms to reset pinion angle. By adjusting the length of your rear control arms you can rotate the axle about its axis to where the diff is perpendicular with the ground, should those angles be acceptable for your driveshaft. Important note here though is that you only want to adjust pinion angle if your driveshaft is at an angle that is inappropriate. The Rezeppa joints in the stock driveshaft need some angle to them to operate happily - the pinion should not be pointed directly at the driveshaft. Pinion angle and driveshaft angle should be off slightly. If you have an aftermarket double cardan to single cardan driveshaft, that angle should be almost 0 - pinion pointed at the driveshaft as much as possible - generally. Almost always exceptions

 

[ScotM]

I am trying to be helpful… but three pages in and there still seems to be some confusion about this. You are talking about pinion angle, but keep asking about the angle of your diff in relation to the ground.
It doesn’t matter what the angle on your diff is. It matters what it is in relation to your driveshaft, ie pinion angle. That is what matters, to line up the driveshaft and eliminate vibration. This will vary a little depending on each build/lift.

So take the advice in this thread, research adjusting pinion angle.

here is one of the first links I

https://www.jlwranglerforums.com/forum/threads/rzeppa-joints-and-rear-pinion-angle.39604/post-884262

thanks, , you have been helpful, and I understand the pinion measurement, and how to measure the pinion angle, and did that already. It is a bit high. My curiosity is around someone else with a mopar 2” lift and stock control arms and stock drive shaft. The angle I have been asking for would be the same on my jeep as theirs. So all things being equal, they could measure their pinion angle with the mopar 2@ lift, or just simply give me the angle of their differential and I would have what I have been requesting. That way I could see what pinion angle mopar was designing in their 2” lift. People assume every bodies an idiot. I’m just using simple geometry to try and make it easier for someone to provide me with what I was asking for, but instead I got lectures on pinion angles, thrust angles track bars and then the rude comments. So moot point, my pinion angle will get put right

the diff-axle are a non-adjustable relationship. So OP I believe is trying to ask in very simple terms for someone, even someone who doesn't understand pinion angle, to just do this simple task and report back. As we do with our kids sometimes it is easier to just ask them to do something wvennif they don't undersrand the why part.

appreciate that. I did measure the pinion angle, and it came out around 4 degrees. I was thinking that if someone else had a mopar 2” lift with everything else stock , including the driveshaft, that the angle I requested should match my differential angle, but at this point I’d take a pinion reading from anyone who has a mopar factory lift. I just want to know what mopar considered an acceptable pinion angle for their lift, and make sure my install of adjustable control arms didn’t eff that up. But I’m going to get the pinion angle back 1-2 degrees anyway. Just curiosity that led to all this..

 

[Mx5red]

thanks, , you have been helpful, and I understand the pinion measurement, and how to measure the pinion angle, and did that already. It is a bit high. My curiosity is around someone else with a mopar 2” lift and stock control arms and stock drive shaft. The angle I have been asking for would be the same on my jeep as theirs. So all things being equal, they could measure their pinion angle with the mopar 2@ lift, or just simply give me the angle of their differential and I would have what I have been requesting. That way I could see what pinion angle mopar was designing in their 2” lift. People assume every bodies an idiot. I’m just using simple geometry to try and make it easier for someone to provide me with what I was asking for, but instead I got lectures on pinion angles, thrust angles track bars and then the rude comments. So moot point, my pinion angle will get put right

appreciate that. I did measure the pinion angle, and it came out around 4 degrees. I was thinking that if someone else had a mopar 2” lift with everything else stock , including the driveshaft, that the angle I requested should match my differential angle, but at this point I’d take a pinion reading from anyone who has a mopar factory lift. I just want to know what mopar considered an acceptable pinion angle for their lift, and make sure my install of adjustable control arms didn’t eff that up. But I’m going to get the pinion angle back 1-2 degrees anyway. Just curiosity that led to all this..

You might get more responses applicable to your question if you named your thread “pinion angle for 2DR mopar 2” lift?”
That way 2dr mopar lift owners might be more likely to click on your thread. Your title just confused people.

 

[AZ Hella]

Have you driven it? Does it have a vibration? Is your OCD off the rails?

 

[Camaroboi13]

So much misinformation in this thread.

As you raise the vehicle, your differential gets further away from the chassis, thus rotating your differential upwards. When this happens, the angle of your driveshaft coming out of your differential changes. That’s the pinion angle. Believe it or not, SHORTENING the length of your lower control arms will reduce the pinion angle and get the driveshaft back in alignment with the front of the driveshaft. Longer lower control arms will increase the pinion angle and that’s when vibrations and failures occur. Shorter LCAs, not longer ones. Don’t worry about where the differential is pointing as long as it’s centered under the vehicle and the driveshaft angle coming out of the differential is as straight as possible.

 

[Remorseless]

So much misinformation in this thread.

As you raise the vehicle, your differential gets further away from the chassis, thus rotating your differential upwards. When this happens, the angle of your driveshaft coming out of your differential changes. That’s the pinion angle. Believe it or not, SHORTENING the length of your lower control arms will reduce the pinion angle and get the driveshaft back in alignment with the front of the driveshaft. Longer lower control arms will increase the pinion angle and that’s when vibrations and failures occur. Shorter LCAs, not longer ones. Don’t worry about where the differential is pointing as long as it’s centered under the vehicle and the driveshaft angle coming out of the differential is as straight as possible.

You don't want to shorten below factory spec on an LCA, as LCAs generally should be used to set wheelbase. You will have to balance UCA/LCA length in order to achieve proper pinion angle while not having any arm fall short of factory length. Generally, with a lifted Jeep, you will need longer LCA and UCA to have the proper amount of additional overhead to adjust pinion angle, with factory length being the bottom end of the range for each.

Also, FYI, 0 angle is not what the OP wants if they're still on the OE Rezeppa joint. From the factory service manual for driveshaft angles:

Under 10* is the target for OE style joints. Rezeppa joints need some angle on them to operate correctly. Too straight and they fail. U-joints (typically aftermarket double cardan "CV") are where you want as little angle as possible.

 

[Camaroboi13]

You don't want to shorten below factory spec on an LCA, as LCAs generally should be used to set wheelbase. You will have to balance UCA/LCA length in order to achieve proper pinion angle while not having any arm fall short of factory length. Generally, with a lifted Jeep, you will need longer LCA and UCA to have the proper amount of additional overhead to adjust pinion angle, with factory length being the bottom end of the range for each.

Also, FYI, 0 angle is not what the OP wants if they're still on the OE Rezeppa joint. From the factory service manual for driveshaft angles:

Under 10* is the target for OE style joints. Rezeppa joints need some angle on them to operate correctly. Too straight and they fail. U-joints (typically aftermarket double cardan "CV") are where you want as little angle as possible.

I like where you’re coming from, almost. I was schooled by a lift company when my 4” lift came with shorter LCAs. Before installing them, I thought maybe I had the fronts and rears mixed up. The guy I spoke to said no, they are correct, call me before you swap the rears out and I’ll show you why.

Without adding upper control arms, your wheel base will be shortened when lifting a vehicle. Your driveshaft is only X” in length, it acts as a pendulum in a sense. So if you’re adding uppers and lowers then you’re extending the length of the driveshaft as well. On 4” of lift already, I’m probably getting close to finding out just how much I’d like that driveshaft to extend. At full articulation, I’m probably asking for trouble.

With lower control arms only, you are keeping the driveshaft length the same as it was before. The trade off as stated before is you lose some wheelbase length.

And when I say flat as possible for driveshaft angle I’m talking about within spec. 1/4”-3/8” shorter LCAs makes a huge difference in pinion angles, more than most would realize until they actually install them. It almost seems not worth all the hassle until you see the difference.

 

[Remorseless]

I like where you’re coming from, almost. I was schooled by a lift company when my 4” lift came with shorter LCAs. Before installing them, I thought maybe I had the fronts and rears mixed up. The guy I spoke to said no, they are correct, call me before you swap the rears out and I’ll show you why.

Without adding upper control arms, your wheel base will be shortened when lifting a vehicle. Your driveshaft is only X” in length, it acts as a pendulum in a sense. So if you’re adding uppers and lowers then you’re extending the length of the driveshaft as well. On 4” of lift already, I’m probably getting close to finding out just how much I’d like that driveshaft to extend. At full articulation, I’m probably asking for trouble.

With lower control arms only, you are keeping the driveshaft length the same as it was before. The trade off as stated before is you lose some wheelbase length.

And when I say flat as possible for driveshaft angle I’m talking about within spec. 1/4”-3/8” shorter LCAs makes a huge difference in pinion angles, more than most would realize until they actually install them. It almost seems not worth all the hassle until you see the difference.

With 4" of lift, on any Jeep - 2 or 4 door - you should be swapping out your OE driveshaft for one of appropriate length. Shortening your LCAs and thus pulling your rear axle further into its arc of travel is a horrible idea. Remember - your rear axle moves forward, towards the front of the vehicle, when lifted vs stock as control arm length hasn't changed. With even shorter LCAs it'll move even your rear axle even further forward.

Which lift company was it? I ask, because I want to be sure to avoid them and never recommend anyone use their product. Any reputable lift company would ensure that with a lifted vehicle you extend the LCAs to put the rear axle back in the proper position in the center of the wheel well, and add adjustable UCAs to correct pinion angle.

 

[DLW]

Hopefully, someone will get you what your asking for. I kind of see where your going with the angles your asking for now, after 4 pages.

rzeppa type driveshafts are not as critical to pinion angle as other u-joint style double cardan DS are.

I have been using about -2 deg down on the pinion with rzeppa style joints with a 2.5" lift and that was close to my stock height pinion setting as I recall, but that little lift would not really require much adjustment to control arms anyway. I used adjustable to better center the tire in the wheel well with bigger tires, then adjust pinion angle from there, as my preference.

 

[ScotM]

So much misinformation in this thread.

As you raise the vehicle, your differential gets further away from the chassis, thus rotating your differential upwards. When this happens, the angle of your driveshaft coming out of your differential changes. That’s the pinion angle. Believe it or not, SHORTENING the length of your lower control arms will reduce the pinion angle and get the driveshaft back in alignment with the front of the driveshaft. Longer lower control arms will increase the pinion angle and that’s when vibrations and failures occur. Shorter LCAs, not longer ones. Don’t worry about where the differential is pointing as long as it’s centered under the vehicle and the driveshaft angle coming out of the differential is as straight as possible.

Super helpful ? thank you

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