Adjusting front axle pinion angle

mrblaine said:
Although Jeep had the low pinion axle from the TJ in production when they switched to the LP axles in the XJ, they still made them the same as the other XJ axles with holes since the rear mount is slotted at the unibody. It stands to reason that they would do the same for the TJ and keep the slots that all other TJ's have even if they were to build a TJ specific front HP 30. Since you have holes, I highly suspect that you have a HP 30 out of an XJ. If you run the VIN on the site that is posted from time to time to get the build sheet, that would tell us one way or the other.
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Mines a '97 - The first few VIN searched I found say they work from '98 on:rolleyes:

XJs are the only common (older) Jeep here, so that's likely it. I'll start crawling under every TJ I see and report back.

Thanks!
 
JoshNZ said:
@mrblaine, yea, probably an unnecessary question, but worth an ask. I'm happy with "it just does"

Re the export model. Im 99% sure that TJs sold in NZ came factory with a Dana 44 rear and a HP Dana 30 in the front. @Kiwi TJ, I'm assuming yours is the same?
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You are correct...as far as I have seen and read all export TJ sports have the 44 rear and 30 front.
Getting the year correct out here is tricky ...The VIN is the best way to sort it out.
Mine was born in 97, landed here in 98, but registered as a 99.:unsure:
 
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@mrblaine, with no surprise, you’re a correct. It’s just a super common swap down here. I guess Dana 44 or any 1ton axles are almost non existent, a HP30 is the best available.
 
Ron Hall said:
About how many turns did it take to make your change. I assume that you worked on all of them.
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Unfortunately I did the adjustment quite a while ago so I don’t recall how many turns it required.

I did end up adjusting both the uppers and lowers and it was quite a bit of adjustment. I recall I tried to balance out the adjustment between the upper/lower as much as I could. I wasn’t anywhere near maxing out the threads on the upper or lower rod ends so it wasn’t too extreme.
 
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Jerry Bransford said:
Absolutely backwards, the pinion angle always (!) takes precedence over the caster angle.

The way to dial it in is to dial in as much caster angle as you can get without the pinion angle getting excessive which causes vibrations. Once you get vibrations from the pinion angle getting excessive, you have to roll back the caster angle until the vibes go away.

The deal with caster angle is that there's no 'precise' caster angle that is needed... you just need 'enough' caster angle to give you good steering return-to-center and stable highway steering. 5 to 5.5 degrees or higher is normally enough, with larger tires not needing as much caster angle for good return-to-center as smaller tires do.
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Easy enough to move the front pinon up with a floor jack, but what about a the instance when it needs to come down. My pinon is 9 and my drive shaft under 5. When I pulled the upper on the driver side, the passenger side was binding and I could not reinstall the drive side even shorten one turn. I finally got the opposite upper off by enlisting my wife and a bar. I am going to look at the effects of jacking either the short or long side of the axle, as was suggested. I also have a heavy duty rachet strap. I would sure like to move that pinion down to plus half or one degree of the ds. I think I need that positive castor also. The back axle was a lot easier just going back and forth between the uppers and using a line up punch.
 
Ok, so Let me try this again, if you have adjustable uppers, you remove the one on the passenger side. Use the one on the driver side to set the pinion angle. Then just install the passenger one so the bolts fit, dont bother making it the same length as the drivers one.

When I tried to post this originally, my screen showed 3 duplicate posts...
 
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I dont know what part is duplicate. My pinon has rotated the wrong direction during the night and jacking on the axle has just made it worse. My bump stops were centered with the lower control arms and now the springs are fighting my attempts to rotate it down. The pinion angle is measured with wheels on the ground but my suspension has fought me ever since I removed the first control arm. My pinion is now about 29 degrees and I was trying to get help without jacking the jeep back up and letting the axle down to remove the coils and starting all over again.
 
I guess with the springs out I could set the uppers to stock length. If brought the angle too far down itvwould probably be easier to raise the pinon.
 
Ron Hall said:
I dont know what part is duplicate. My pinon has rotated the wrong direction during the night and jacking on the axle has just made it worse. My bump stops were centered with the lower control arms and now the springs are fighting my attempts to rotate it down. The pinion angle is measured with wheels on the ground but my suspension has fought me ever since I removed the first control arm. My pinion is now about 29 degrees and I was trying to get help without jacking the jeep back up and letting the axle down to remove the coils and starting all over again.
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Do you have both uppers off? 29 degrees? As recommended make pinion adjustments using only one of the upper arms. Once you have it set adjust the other to fit and install it.
 
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Ron Hall said:
I dont know what part is duplicate. My pinon has rotated the wrong direction during the night and jacking on the axle has just made it worse. My bump stops were centered with the lower control arms and now the springs are fighting my attempts to rotate it down. The pinion angle is measured with wheels on the ground but my suspension has fought me ever since I removed the first control arm. My pinion is now about 29 degrees and I was trying to get help without jacking the jeep back up and letting the axle down to remove the coils and starting all over again.
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I am fighting a similar problem right now. Blaine walked me through it some.


Jack the jeep, leave the springs in.
put jack stands under the frame to support the jeep, lower the axle
remove upper passenger arm
Use the drivers side to adjust the pinion angle. This one may fight you a little because there is a little pressure. if you need pinion down shorten the arm, if you need pinion up lengthen.
I just pull the bolt out, turn the adjuster in or out as needed, then push the bolts back in, using a drift to align the bushings/rod ends. I dont tighten them yet
Jack the jeep back up, put jack stands under axle, lower jeep onto the stands under the axle.
Check the alignment of the driveshaft.
The pinion agle needs to be within 1 degree of the driveshaft
Repeat as necessary until you get the pinion where it needs to be.
then tighten up the UCA bolts on the drivers side. Double check the angles, if it is good, then install the passenger side by adjusting it until the bolts align up without forcing the axle angle, it may need the drift to get through the bushing.
Tighten up the passenger UCA, double check driveshaft angle, if it is good, remove jeep from jackstands.
 
astjp2 said:
Ok, so Let me try this again, if you have adjustable uppers, you remove the one on the passenger side. Use the one on the driver side to set the pinion angle. Then just install the passenger one so the bolts fit, dont bother making it the same length as the drivers one.

When I tried to post this originally, my screen showed 3 duplicate posts...
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Don't overlook the preload.
 
mrblaine said:
Don't overlook the preload.
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If he has single adjustable uppers and removes the passenger upper he will also have to remove one end of the driver upper to adjust it, at which time both uppers will be off. Where should the floor jack be supporting the diff when both uppers are disconnected? Something has to relieve the preload of the driver upper in order to unbolt it.

Also, doesn't the jeep need to be at ride height to adjust the pinion angle properly?
 
bobthetj03 said:
If he has single adjustable uppers and removes the passenger upper he will also have to remove one end of the driver upper to adjust it, at which time both uppers will be off. Where should the floor jack be supporting the diff when both uppers are disconnected? Something has to relieve the preload of the driver upper in order to unbolt it.

Also, doesn't the jeep need to be at ride height to adjust the pinion angle properly?
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No, you make the adjustments using one arm and that arm has to be on the rig holding the load that compresses the bushing or joint. So no support at ride height. Once the adjustment has been done, then relieve the pressure by jacking up under the tie rod until you turn the bolt with your fingers. Then you bring the other arm to the hole length needed with the rig level and at ride height.

Spring perches overhang the front of the axle tube and cause the uppers to be in tension or pulled on. Jacking up under the spring perch or tie rod counteracts that force.
 
mrblaine said:
No, you make the adjustments using one arm and that arm has to be on the rig holding the load that compresses the bushing or joint. So no support at ride height. Once the adjustment has been done, then relieve the pressure by jacking up under the tie rod until you turn the bolt with your fingers. Then you bring the other arm to the hole length needed with the rig level and at ride height.

Spring perches overhang the front of the axle tube and cause the uppers to be in tension or pulled on. Jacking up under the spring perch or tie rod counteracts that force.
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My brain must be on vacation because I'm missing something in this process. Are we assuming here that we have double adjustable arms?
 
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