Adjusting front axle pinion angle


Took the tj out and drove it about 30 miles. Steering was improved and no vibration. When I got back, angles had changed slightly. Front pinion is 8.2 on both flats. Front drive shaft is 7.5. I had shortened the frontvlowers one turn when i installed the JJ washers because i didn’t know how much I was going to be able lengthen the uppers. I am going to lengthen the lowers back that one turn because they turn easily. Maybe I can get a couple of tenths reduction on that pinion angle.

Rear pinion is 10.1 and drive shaft is 11.7. I need to study that, but those contol arms all turn easily. I want to thank everyone on this forum for all the help.
 
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I just installed a Tom Woods front driveshaft last night. I think I’m getting a slight vibration that starts around 65mph. If I measure my angles correctly my pinion is 8 and my driveshaft is 11. Is this most likely the culprit on my vibration? May need to get adj upper arms as I only have adj lower arms currently.
 
I just installed a Tom Woods front driveshaft last night. I think I’m getting a slight vibration that starts around 65mph. If I measure my angles correctly my pinion is 8 and my driveshaft is 11. Is this most likely the culprit on my vibration? May need to get adj upper arms as I only have adj lower arms currently.
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Getting your front driveshaft and pinion angles closer should solve your problem, at least it did for me.

Can you make the necessary angle adjustments with only the lowers? When I adjusted my rear pinion angle, mine differed a few degrees like yours. It only took one and a half revolutions of my rear upper control arms, to get the angle I needed. Using the thread pitch of the jam nuts, this works out to about 3/16" difference in length. I don't know how 3/16" will effect on you castor angle.

I didn't have any vibration in my LJ after 3" lift, until I regeared. After I regeared, transfer case skid spacers and adjustable rear uppers allowed me to adjust the rear pinon/driveshaft angles. This took care of most of the vibration. I removed the spacers and installed a SYE and new driveshaft in the rear, but still had a slight vibration from the front. I rebuilt the front driveshaft and my vibration was gone.

I measured both front and rear pinion and driveshaft angles. They are the same or within a degree of each other (front pinion to front driveshaft/rear pinion to rear driveshaft). I don't have a digital angle gage. I use a simple angle gage with a needle, and a magnifying glass the read between the lines.
 
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LukesfirstJeep said:
Getting your front driveshaft and pinion angles closer should solve your problem, at least it did for me.

Can you make the necessary angle adjustments with only the lowers? When I adjusted my rear pinion angle, mine differed a few degrees like yours. It only took one and a half revolutions of my rear upper control arms, to get the angle I needed. Using the thread pitch of the jam nuts, this works out to about 3/16" difference in length. I don't know how 3/16" will effect on you castor angle.

I didn't have any vibration in my LJ after 3" lift, until I regeared. After I regeared, transfer case skid spacers and adjustable rear uppers allowed me to adjust the rear pinon/driveshaft angles. This took care of most of the vibration. I removed the spacers and installed a SYE and new driveshaft in the rear, but still had a slight vibration from the front. I rebuilt the front driveshaft and my vibration was gone.

I measured both front and rear pinion and driveshaft angles. They are the same or within a degree of each other (front pinion to front driveshaft/rear pinion to rear driveshaft). I don't have a digital angle gage. I use a simple angle gage with a needle, and a magnifying glass the read between the lines.
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I thought about just trying to shorten my lowers but wasnt sure. I have no idea what my castor angle is currently. It could be way off already.
 
I thought about just trying to shorten my lowers but wasnt sure. I have no idea what my castor angle is currently. It could be way off already.
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After I removed my transfer case skid spacers, with OEM upper front control arms and Zone non adjustable lower front control arms, my pinon/driveshaft angles are equal. This is with 3" Zone springs installed.

I never measured my front pinion angle with the transfer case spacers in place. I don't know what my castor is, but my steering wheel "return to center" seems OK.
 
LukesfirstJeep said:
After I removed my transfer case skid spacers, with OEM upper front control arms and Zone non adjustable lower front control arms, my pinon/driveshaft angles are equal. This is with 3" Zone springs installed.

I never measured my front pinion angle with the transfer case spacers in place. I don't know what my castor is, but my steering wheel "return to center" seems OK.
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I just adjusted my lowers 2 full turns shorter and got the angles, pinion 9.7 and driveshaft 10.6. I bought an electric angle finder to be more accurate. I still have a slight vibration but not till 70 now. Not sure I want to adjust my lowers shorter or not. I might be able to get one more turn shorter or of them.
 
Jerry Bransford said:
Worry less about the caster angle and more about the pinion angle. Read Blaine's post immediately above again. The front pinion angle absolutely cannot be too low as it appears yours is.
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so basically if there is an offset in the angle, it's ok if the angle is "pushing UP" vs it "falling down" (sorry, it all makes sense but i'm a visual person). About to try full alignment on a 2000 TJ that seems to have the castor lower than the pinion, the axle on a slight angle (passenger side sits back almost an inch) and a little wobble at 45mph to round it all out.
 
I didn't follow most of that aside from you're going to attempt your own alignment and that the front axle is not square to the frame/parallel to the rear axle.

Caster (not castor, which is a bean) angle take precedence over the front axle's pinion angle. The goal should be to have as much caster as is possible without so much that it causes the front driveshaft's front u-joint to vibrate from excessive pinion angle. Raise the caster angle until you get driveshaft u-joint vibration then back off the caster angle just enough to stop the vibration.

But before adjusting the caster angle though, adjust the front control arms so the axle is square.
 
Jerry Bransford said:
I didn't follow most of that aside from you're going to attempt your own alignment and that the front axle is not square to the frame/parallel to the rear axle.

Caster (not castor, which is a bean) angle take precedence over the front axle's pinion angle. The goal should be to have as much caster as is possible without so much that it causes the front driveshaft's front u-joint to vibrate from excessive pinion angle. Raise the caster angle until you get driveshaft u-joint vibration then back off the caster angle just enough to stop the vibration.

But before adjusting the caster angle though, adjust the front control arms so the axle is square.
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Jerry Bransford said:
I didn't follow most of that aside from you're going to attempt your own alignment and that the front axle is not square to the frame/parallel to the rear axle.

Caster (not castor, which is a bean) angle take precedence over the front axle's pinion angle. The goal should be to have as much caster as is possible without so much that it causes the front driveshaft's front u-joint to vibrate from excessive pinion angle. Raise the caster angle until you get driveshaft u-joint vibration then back off the caster angle just enough to stop the vibration.

But before adjusting the caster angle though, adjust the front control arms so the axle is square.
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yeah... im sure I didn't explain that first part all that intelligently... but thanks, I will take care of the axle first, then work thru the rest.
2000TJ w a 6" lift, 3-link, and 35" tires. along w picts attached.... what's your thought of where I am with the angles, and where I should hope to be. Thanks. she drives straight(although I guess a little like a crab w frame issue), and little wobble at 45.

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