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Unread 03-21-2012, 05:25 AM   #1
BioTex
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Adjustable upper or lowers to correct pinion angle?

Trying to get a better understanding on pinion angle adjustment, and in my mind I was thinking the lowers were used to adjust pinion angle. Then I read a few threads that mentiond adjustable uppers

Which is it, and why?

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'85 CJ7, BDS 4" lift, 1" Body lift, 33x12.5, Shrockworks Sliders, 304 V8 with RV cam., T-176, D300, Dana 30, AMC 20.
1986 CJ10-A SD-33 Diesel/727/np208
1971 800B with 345/T-19
06' TJ Rubicon, 4" R.C. springs, BFG/AT 35s M.C. 6" fenders, rockers and surrounds, Currie front & rear adj. tracbars, tattons DC rear shaft, adj. upper - lower CA's. Bilstein 5100's
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Unread 03-21-2012, 06:40 AM   #2
hulud44
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Uppers. To adj pinion angle for a lifted suspension you will need to rotate the axle so the diff cover is pointed further down towards the ground which in turn points the DS yoke up for proper alinement. (caster angle). To do that its better to make the uppers longer rather than shorten the lowers. Of course its best to have all adjustables to be a little more exact.
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Unread 03-21-2012, 06:47 AM   #3
BioTex
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Then if you only adjust the uppers, will the tire still be centered under the wheel well, or is the adjustment too minor to matter?

Edit: BTW, I'm talking about the rear pinion. I'm switching to a CV shaft...
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'85 CJ7, BDS 4" lift, 1" Body lift, 33x12.5, Shrockworks Sliders, 304 V8 with RV cam., T-176, D300, Dana 30, AMC 20.
1986 CJ10-A SD-33 Diesel/727/np208
1971 800B with 345/T-19
06' TJ Rubicon, 4" R.C. springs, BFG/AT 35s M.C. 6" fenders, rockers and surrounds, Currie front & rear adj. tracbars, tattons DC rear shaft, adj. upper - lower CA's. Bilstein 5100's
YJ Buggy Build Current project. Stroker/FI ?
1990 MJ Comanche 4.0L AX15/np231
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Unread 03-21-2012, 06:55 AM   #4
hulud44
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It depends on how much your lifted and how off your pinion angle is. It really shouldnt be that large of an adjustment. Unless your talking about some extreme mod like stretching wheel base for very large rubber. In that case there a whole different set of issues to deal with.
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Unread 03-21-2012, 06:58 AM   #5
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Go to YouTube and search "Teraflex." They have a nice 3 part video series on doing an alignment on a TJ. The TJ they use has adj arms and they go over how it all works.
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Unread 03-21-2012, 07:12 AM   #6
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Both. Assigning 'duties' to the uppers or lowers makes no sense. You need adjustment all around if you are planning on placing the axle where it needs to be to avoid interference while also running proper pinion angle.
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Unread 03-21-2012, 07:23 AM   #7
BioTex
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Excellent video. Thanks for the tip.
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'85 CJ7, BDS 4" lift, 1" Body lift, 33x12.5, Shrockworks Sliders, 304 V8 with RV cam., T-176, D300, Dana 30, AMC 20.
1986 CJ10-A SD-33 Diesel/727/np208
1971 800B with 345/T-19
06' TJ Rubicon, 4" R.C. springs, BFG/AT 35s M.C. 6" fenders, rockers and surrounds, Currie front & rear adj. tracbars, tattons DC rear shaft, adj. upper - lower CA's. Bilstein 5100's
YJ Buggy Build Current project. Stroker/FI ?
1990 MJ Comanche 4.0L AX15/np231
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Unread 03-21-2012, 08:03 AM   #8
BioTex
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I finished watching the 3 teraflex videos, and the guy adjusted the lowers to raise the rear pinion. The only time he adjusted the uppers was to move the whole axle to the rear.

So, what I'm seeing is to first adjust the lowers. He was demonstrating with a long arm triangulated kit (no track bar), but I am going to assume it is the same for a short arm?

I currently have the fixed uppers, and don't want to have to replace them, but will if that is the better option. So I am confused why a lot of the other threads I read state to adjust the uppers. Just wanting a little clarification as to why the discrepecies.

As IMPED stated, I can see the need to adjust both, but mainly the lowers for correcting the pinion angle.
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'85 CJ7, BDS 4" lift, 1" Body lift, 33x12.5, Shrockworks Sliders, 304 V8 with RV cam., T-176, D300, Dana 30, AMC 20.
1986 CJ10-A SD-33 Diesel/727/np208
1971 800B with 345/T-19
06' TJ Rubicon, 4" R.C. springs, BFG/AT 35s M.C. 6" fenders, rockers and surrounds, Currie front & rear adj. tracbars, tattons DC rear shaft, adj. upper - lower CA's. Bilstein 5100's
YJ Buggy Build Current project. Stroker/FI ?
1990 MJ Comanche 4.0L AX15/np231
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Unread 03-21-2012, 08:08 AM   #9
geiman
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Quote:
Originally Posted by BioTex View Post
I finished watching the 3 teraflex videos, and the guy adjusted the lowers to raise the rear pinion. The only time he adjusted the uppers was to move the whole axle to the rear.

So, what I'm seeing is to first adjust the lowers. He was demonstrating with a long arm triangulated kit (no track bar), but I am going to assume it is the same for a short arm?

I currently have the fixed uppers, and don't want to have to replace them, but will if that is the better option. So I am confused why a lot of the other threads I read state to adjust the uppers. Just wanting a little clarification as to why the discrepecies.

As IMPED stated, I can see the need to adjust both, but mainly the lowers for correcting the pinion angle.
You're seeing discrepancies because as Imped already stated, the uppers and lowers don't have set functions. Shortening the lowers will raise the pinion but also shorten wheel base; extending the uppers raises the pinion but increases wheel base. And of course the converse applies. To properly set your pinion and place the axle, you'll want both upper and lower adjustable arms. You can try to get away with only one set of adjustables, but you might not be able to get things properly set.
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Unread 03-21-2012, 08:11 AM   #10
del_TJ
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I'm running adjustable rear lower arms with stock uppers to correct pinion angle on a 3" lift. As IMPED said, it's best to have both adjustable lower and uppers to dial it in correctly. But, if I had to choose, I'd start with the lowers b/c that's enough to adjust the angle (in my case anyway) and they're the ones that get dragged on the rocks. A drawback is that shortening your lower arms only will shorten your wheelbase.
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Unread 03-21-2012, 01:21 PM   #11
BioTex
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Quote:
Originally Posted by geiman View Post
You're seeing discrepancies because as Imped already stated, the uppers and lowers don't have set functions. Shortening the lowers will raise the pinion but also shorten wheel base; extending the uppers raises the pinion but increases wheel base. And of course the converse applies. To properly set your pinion and place the axle, you'll want both upper and lower adjustable arms. You can try to get away with only one set of adjustables, but you might not be able to get things properly set.
Quote:
Originally Posted by del_TJ View Post
I'm running adjustable rear lower arms with stock uppers to correct pinion angle on a 3" lift. As IMPED said, it's best to have both adjustable lower and uppers to dial it in correctly. But, if I had to choose, I'd start with the lowers b/c that's enough to adjust the angle (in my case anyway) and they're the ones that get dragged on the rocks. A drawback is that shortening your lower arms only will shorten your wheelbase.
Much thanks for clearing up those muddy waters for me!
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'85 CJ7, BDS 4" lift, 1" Body lift, 33x12.5, Shrockworks Sliders, 304 V8 with RV cam., T-176, D300, Dana 30, AMC 20.
1986 CJ10-A SD-33 Diesel/727/np208
1971 800B with 345/T-19
06' TJ Rubicon, 4" R.C. springs, BFG/AT 35s M.C. 6" fenders, rockers and surrounds, Currie front & rear adj. tracbars, tattons DC rear shaft, adj. upper - lower CA's. Bilstein 5100's
YJ Buggy Build Current project. Stroker/FI ?
1990 MJ Comanche 4.0L AX15/np231
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