Pinion Angle Help / Clarification...

[Infidel Edition]

I read 4.3LXJ's thread: http://www.xjtalk.com/showthread.php?t=7299 and it made sense mostly.
I did the RE 4.5" springs in the rear and rocked and shucked and jived to try to get everything to settle.
Then took the measurements and have thus (red is true vertical and horizontal - blue is actual off true):

3978

1st
... the back of the TCase angles down 1*
... the pinion angles up 3 or 4 *
so I need a 1.5* to 2* axle shim to my axle counter clockwise in the pic above to move that closer to a 1* up?
~ what's the pinion tolerance before there's an issue? ie. is 2* acceptable? I drive highway speeds of 75 mph regularly. But need to deal with the exhaust before I go out and see what she does.

2nd
the drive line is 15* off true horizontal or 14* off the back of the TCase.
What's the tolerance?
.................It's an '89 5 speed with the stock D35 rear. As I understand, the most tolerant drive line of drive line angles......

Or am I totally lost now?

[Infidel Edition]

found a pair of 1.5° shims for $53
...but ordered the Tuff Country (on Amazon) 2° set for $23

will recheck torque and double che k the °'s before installing

[4.3LXJ]

Yes, the idea is to match the tcase flange and pinion angles as close as possible

[Infidel Edition]

wait... I want the pinion's up angle to the TCase's down angle...
so reduce the 3° - 4° to a 1° means a 2° shim or a 3° shim...

so the 2° I ordered will give me a TCase down angle of 1° and a pinion up angle of 1° - 2°
making the two within a degree of each other...

so a 2.5° would have been better if they came in 1/2° sizes?

...damn auto correct

[4.3LXJ]

2° will be close enough

[Infidel Edition]

2° will be close enough

awesome
thanks

...must have posted at the same time. didn't see your post before the last

[Infidel Edition]

2° will be close enough

Steve,
.....I need to remeasure as I think I was on a slight incline with the e-brake engaged. Not sure if that would cause that much rotation of the axle. But will make sure it's free and some chalks under the front wheels to keep it stationary.

So, most of the write-ups say to use the actual seat of the u-joint on the pinion side.
I used the flat surface here and a piece of angle iron.
3981
.....same spot on t-case as well.

Since I'm going to "measure twice" out of anal-retentiveness, is that a good spot?

[4.3LXJ]

That would get it close. But I use the flat surface on the pinion yoke. You need that angle relative to vertical. The fill bolt on the tcase is a good flat surface and will be the same as on the yoke. It is not how much the joint flexes, it is how it measures relative to vertical. You need the same reference for both joints

[Infidel Edition]

Note for anyone that may come across this thread, the math of a T-Case Drop should adjust the drive line angle about 1 degree for each 1/2 inch of case drop.

... or increase it by 1 degree for each 1/2" of axle drop.

* rough estimate

thus a 2" spring lift should increase the drive line angle by 1 degree...

** solely based on the geometry associated.

[Infidel Edition]

That would get it close. But I use the flat surface on the pinion yoke. You need that angle relative to vertical. The fill bolt on the tcase is a good flat surface and will be the same as on the yoke. It is not how much the joint flexes, it is how it measures relative to vertical. You need the same reference for both joints

My parking brake on a hill reference was in relation to any torsional (is that a real word?) adjustment caused by the e-brake against the hill... vs. no gravity pull in relation to chock blocks under the front wheels.

[4.3LXJ]

OK

But I want to say to all those who are looking for rules of thumb. Measure, measure measure. The reason is that there are small differences in lift kit rear springs, then throw in some extended shackles and you can start tossing rules of thumb out. What I wanted in this thread is to demonstrate how the professionals do it so that anyone can set up their drivelines regardless of what has been done to lift the rig. After all you might have done one of my kind of lift kits where parts are either scrounged or made by me. :D

[Infidel Edition]

OK

But I want to say to all those who are looking for rules of thumb. Measure, measure measure. The reason is that there are small differences in lift kit rear springs, then throw in some extended shackles and you can start tossing rules of thumb out. What I wanted in this thread is to demonstrate how the professionals do it so that anyone can set up their drivelines regardless of what has been done to lift the rig. After all you might have done one of my kind of lift kits where parts are either scrounged or made by me. :D

So I was digging around while waiting for my shims to show...
Above, where I mention the 1 degree per 1/2" axle drop, I mean on the drive shaft.
NOT PINION ANGLE
2 separate angles that people get confused (from what I gather in reading).
The pinion angle needs to be measured after the lift to get it to match the TCase angle.
The Drive Line angle off the TCase is another angle ~ which as far as I gather shouldn't exceed 20 degrees.
Thus, in my lift, my drive shaft is 14 degrees off the TCase. if I lift it 2" more inches, the drive shaft angle would become 15 degrees. But that may or may not have any effect on my pinion angle.

Is that better spoken?

[4.3LXJ]

Yup

[denverd1]

Howdy fellers. I'm on the fence on going up another 2" all around (I have the parts laying around in my garage). So if you use shackles to get another 2" out of the rear - and I desperately need to, stiff as can be - does that change the geometry of the shims? In my mind, the 2" drop in rear leaf mount would point the 3rd member up toward the hood? I realize I need to measure my angles once lifted...

So i'll be at 6" with 2" shackle in the back. currently no shims, would that put me looking for 4* shims?

[4.3LXJ]

Right on Denver, it does change 1° with each inch of shackle length. So with a shackle four inches longer than you have, it will change it 4°

[bluedragon436]

I'm just hoping the 6˚ shims I ordered with my lift components works for my setup.. Was looking online and talked to IRO about it, and they recommended 6˚ for the 6.5" setup w/ adj shackles.. and especially when running the SYE.. if not, then I guess we'll go from there if I have vibes.. Got to get a front shaft out of an XJ to rebuild so I can install it once I do the SYE, if nothing else for temp use, till I can get the proper measurements and get a new shaft made...

[4.3LXJ]

It might work. But you may find you would be happier with the 4°. But the bottom line is that it has to be within 4° of being correct or it will vibrate

[denverd1]

yea, I need a back-up as well. LOL first time we went wheeling I was still driving the jeep to and from parks. I heard a clickety click as we pulled out of Gilmer, 70 miles from the house. It made it all the way to my neighborhood before the front shaft crapped out and started making all sorts of rackets as it bounced off the crossmember, exhaust and everything else.

I've been hesitant to go higher cause I was never confident I had my driveline angles setup right. Gonna get some shims and LIFT that puppy a few more!!

[bluedragon436]

It might work. But you may find you would be happier with the 4°. But the bottom line is that it has to be within 4° of being correct or it will vibrate

Yeah that is what I'm worried about.. Kind of wishing I had purchased a set of 4˚ shims as well.. But figure I'm ordering some missing hardware from them, so might just go ahead and pick up a set of 4˚ shims to have them just in case...

[4.3LXJ]

Here is the info you need. Only difference is now I use a smart phone with a leveler app instead of an angle finder

http://www.xjtalk.com/showthread.php?t=7299

[bluedragon436]

Yeah saw that thread Steve... and def plan on using it to check my angles once I get the new lift parts installed.. Want to try and make sure it's all good from the get go, before I have to deal with the vibes... at least that's the plan...