Front pinion angle questions

Ron Hall

Ron Hall

TJ Enthusiast
Joined
Nov 14, 2018
Messages
310
Location
Arkansas
Looking at my pinion angles after reducing my suspension lift on my 06 Rubicon. My sears angle finder is a little crude. I looked into the possibility of an electronic one. I ended up installing a tremac free app on my iPhone 7+ . It seems accurate and corresponds pretty well with the sears angle finder. It is a lot easier to read. It would be nice to compare with a digital if anyone has one and a iphone.
Looks like my front pinion is about 11.5 and my front drive shaft is about 7.5. I am getting some vibration and I think I need more caster for the steering. Can I bring that pinon down to the shaft angle? I would like to get that pinon angle right and then get an alignment check.
 
Ron Hall said:
Looking at my pinion angles after reducing my suspension lift on my 06 Rubicon. My sears angle finder is a little crude. I looked into the possibility of an electronic one. I ended up installing a tremac free app on my iPhone 7+ . It seems accurate and corresponds pretty well with the sears angle finder. It is a lot easier to read. It would be nice to compare with a digital if anyone has one and a iphone.
Looks like my front pinion is about 11.5 and my front drive shaft is about 7.5. I am getting some vibration and I think I need more caster for the steering. Can I bring that pinon down to the shaft angle? I would like to get that pinon angle right and then get an alignment check.
Click to expand...
The jeep does have a 1” mml. I think I will have to pull the read dc driveshart to get thise angles
 
If I recall correctly the front driveshaft is a double cardan. The pinion angle should be as close to the driveshaft angle as feasible. Ideally you want it to be about 0.5 to 1 degree above or below to ensure the lower u-joint stays properly lubricated.
 
Also any extra that you want for axle movement during high torque moments such as rock crawling or Saturday night drag racing. I end up setting mine at about 1-1.25 degrees down in the back.
 
astjp2 said:
.5 up on the front driveshaft, .5 down in the rear is common.
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Careful here. If you set your pinion above DS angle on a taller lift you won’t have enough caster.
My rig with 3.5” lift. Front is set 2* below front DS angle. On my Jeep that only leaves 4.5 caster. If I went even or above DS I would have any caster left.
I would set it at factory caster, then adjust it up just enough to eliminate the vibrations.
What lift height you running?
 
Ron Hall said:
Looking at my pinion angles after reducing my suspension lift on my 06 Rubicon. My sears angle finder is a little crude. I looked into the possibility of an electronic one. I ended up installing a tremac free app on my iPhone 7+ . It seems accurate and corresponds pretty well with the sears angle finder. It is a lot easier to read. It would be nice to compare with a digital if anyone has one and a iphone.
Looks like my front pinion is about 11.5 and my front drive shaft is about 7.5. I am getting some vibration and I think I need more caster for the steering. Can I bring that pinon down to the shaft angle? I would like to get that pinon angle right and then get an alignment check.
Click to expand...
Lower your front pinion to line up with your ds. Once you lower the pinion the axle angle will most likely change so keep your eyes on both angles. If you get vibs start raising it in .5 increments.
 
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Front driveshaft vibrations are caused by trying for too much caster angle which has created an excessive pinion angle which is the root cause of the vibrations.

Pinion angle always takes precedence over caster angle. Always. The correct way to achieve optimal angle where both are concerned are to raise the caster angle until you get vibrations then back off until the vibrations go away.
 
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Jerry Bransford said:
Front driveshaft vibrations are caused by trying for too much caster angle which has created an excessive pinion angle which is the root cause of the vibrations.

Pinion angle always takes precedence over caster angle. Always. The correct way to achieve optimal angle where both are concerned are to raise the caster angle until you get vibrations then back off until the vibrations go away.
Click to expand...
Well said. But can be confusing to some people. What direction does the pinion move to increase or decrease caster? I think that’s what confuses people.
 
Pinion up = decreased castor

Pinion down = increased castor

7 degrees castor is optimal. Too little leads to unstable steering/ wobble.

If you can’t get pinion high enough and still have enough caster, the Cs have to be cut, rotated, and welded back on.
 
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Gollywomper said:
Well said. But can be confusing to some people. What direction does the pinion move to increase or decrease caster? I think that’s what confuses people.
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Lowering the pinion angle increases caster angle. Caster angle is increased by shortening the upper control arm/lengthening the lower control arm.

The larger the tire size, the less caster angle that is required to obtain good return-to-center and good steering stability. LIke for 35" tires, you can get away with 5.5 to 6 degrees and have good steering qualities.

83553
 
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Running your pinion above the drive shaft angle shouldn’t be done unless absolutely necessary. It reduces your caster angle significantly. Each Jeep is a bit different. But on a 4” lift if you run pinion angle above the DS angle you will have very low caster angle.
 
Jerry Bransford said:
Front driveshaft vibrations are caused by trying for too much caster angle which has created an excessive pinion angle which is the root cause of the vibrations.

Pinion angle always takes precedence over caster angle. Always. The correct way to achieve optimal angle where both are concerned are to raise the caster angle until you get vibrations then back off until the vibrations go away.
Click to expand...
The rear is worse than the front. The ds angle is 7.6 and the pinon is 14.0. If I read one of you previous posts, the pinon should align with the ds.
83562
 
Ron Hall said:
The rear is worse than the front. The ds angle is 7.6 and the pinon is 14.0. If I read one of you previous posts, the pinon should align with the ds. View attachment 83562
Click to expand...

Just about aligned. 0.5 deg down. My rear is about 17 degrees up. But no caster to worry about, just spring and shock mounts and track bar brackets.

Mine was an axle swap so my 17 deg up didn’t have those concerns.
 
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I think front will also benefit from bringing the pinon down closer to ds angle. That should increase caster and steering. I will have alignment checked at that point.
 
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Jerry Bransford said:
Front driveshaft vibrations are caused by trying for too much caster angle which has created an excessive pinion angle which is the root cause of the vibrations.

Pinion angle always takes precedence over caster angle. Always. The correct way to achieve optimal angle where both are concerned are to raise the caster angle until you get vibrations then back off until the vibrations go away.
Click to expand...
I will be making a pretty good step in pinion angle fromt and rear. Approximately how much change will I get out of one turn out on the lowers and in on the uppers?
 
My first look at adjusting the lower rear is that the lowers will come out of the axle bracket much easier than the frame brackets. Also looks like the bolt is in backwards and may be a struggle to get out without removing the wheel. I am sure it will be easier to move things around with wheels on the ground. Any insights?
 
Ron Hall said:
My first look at adjusting the lower rear is that the lowers will come out of the axle bracket much easier than the frame brackets. Also looks like the bolt is in backwards and may be a struggle to get out without removing the wheel. I am sure it will be easier to move things around with wheels on the ground. Any insights?
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Wheels on the ground is easiest. You can remove 1 arm at a time and still be safe.

I believe my arms did about .5 for every full turn but since mine are double adjustable I wasn't paying to close of attention.
 
Alex01 said:
Wheels on the ground is easiest. You can remove 1 arm at a time and still be safe.

I believe my arms did about .5 for every full turn but since mine are double adjustable I wasn't paying to close of attention.
Click to expand...
Those double adjustables would be nice.
 
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