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Old 03-21-2018, 05:49 PM
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Caster/Pinion Angles on new front axle install

So I just had a Dana Ultimate 44 axle installed in my 2016 2-door JK. It replaced the Dana 30 that was in there (Willys Wheeler). I already have a JKS 2.5" JSpec lift and J-link LCAs. I had an earlier post asking about whether the J-Link arms, which already correct caster, would be overcorrecting the caster angle in this application, since the Ultimate 44 also has some caster/pinion angle correction built in.

So I drove it back from the shop, I had to correct the steering wheel a bit because it was off. Either they forgot to correct it or just missed the mark a bit but that is an easy fix. The steering feels much heavier, as would be expected with more caster. The steering wheel doesn't return to center very well around corners (also an issue of too much caster angle). It's not horrible, but what I want to know is if it is dangerous or will cause premature wear. Also I should point out that I haven't done an alignment yet.

I got out my iphone angle-finder in the garage to check some angles. The floor measures level so the other angles should not be affected by that. My front driveshaft is at -4 degrees downhill from the transfer case to the pinion of the U44. The machined circles on the front of the differential measure -1 degrees (or 91 degrees relative to the floor). So the driveshaft is at 3 degrees relative to the pinion. I'm not sure if someone could tell me anything based on these measurements.

I am planning on getting the front end aligned. However my question is whether I should swap out the front JKS LCAs for the stock ones. I think this will fix the caster problem by tilting the differential slightly forward (shorter arms), and the driveshaft will wind up at or close to +/- 1 degree? I'm not sure how many degrees of correction it will do. Or I could leave the JKS LCAs in there, get it aligned and live with the caster that it has until I can get some adjustable upper control arms. What do you guys think? I guess I'd rather not do all the work of pulling and replacing the LCAs but if it is a safety or wear issue (I was told caster is NOT a wear angle?) then I suppose I should do it.

To throw a real wrench into things, we are planning on doing a pretty good 2 week overland trip to death valley/mojave desert/joshua tree, and wanted to leave either this weekend or monday so I need to get the jeep ready for that ASAP. Thanks for any advice.

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Old 03-21-2018, 11:41 PM   #2
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Better to have too much caster than not enough. Going straight on the freeway and in the dirt you won't notice it much. At least you won't have vibes in the driveshaft due to bad U joint angle. Have a good 4x4 shop do the alignment.
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2014 JKUR, Leather and everything inside, 4 inch OME springs, all Alpine arms, Adams front driveshaft, Falcon 2.1's, Adj track bars front and rear, heavy bumpers and winch, ICON rims and 315-70-17 BFG KO2's, ARB diff covers, ProComp LED's, 2 Bernese Mtn dogs.
Previously 2001 XJ lifted 5, SYE, True-tracks F & R.
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Old 03-23-2018, 07:40 AM   #3
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You need to know the total caster/pinion offset of the housing. That is, the total angle between Caster and pinion angle combined. Stock is 6 degrees (4 degrees caster, two degrees on the pinion), while most of the aftermarket "angle corrected" housing are around 10. If you know the total offset you can determine the approximate caster angle by doind as you have, determining the pinion angle off the front cover bolts, or the "O" castings on the housing. My hunch from what you posted, you have way too much caster.
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Old 03-23-2018, 11:51 AM
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Originally Posted by SoK66 View Post
You need to know the total caster/pinion offset of the housing. That is, the total angle between Caster and pinion angle combined. Stock is 6 degrees (4 degrees caster, two degrees on the pinion), while most of the aftermarket "angle corrected" housing are around 10. If you know the total offset you can determine the approximate caster angle by doind as you have, determining the pinion angle off the front cover bolts, or the "O" castings on the housing. My hunch from what you posted, you have way too much caster.
Problem is Dana doesn't publish that spec... I did some digging on the internet, seems like it's maybe around 9. Anyway I ordered some adjustable uppers to fix it.
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Old 03-23-2018, 12:16 PM   #5
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I would guess that if you set your front pinion up at 4* with some adjustable front CA's you would be close. Any alignment shop can check caster.
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2014 JKUR, Leather and everything inside, 4 inch OME springs, all Alpine arms, Adams front driveshaft, Falcon 2.1's, Adj track bars front and rear, heavy bumpers and winch, ICON rims and 315-70-17 BFG KO2's, ARB diff covers, ProComp LED's, 2 Bernese Mtn dogs.
Previously 2001 XJ lifted 5, SYE, True-tracks F & R.
CJ7, 304V8, auto, loaded, Detroit rear, and more.
90 Bronco,, 76 Bronco,, 70 Bronco
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Old 03-23-2018, 12:53 PM
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I would guess that if you set your front pinion up at 4* with some adjustable front CA's you would be close. Any alignment shop can check caster.
Thanks, I think that is what I will shoot for. I haven't had a jeep aligned at a shop before and the 4x4 shop I usually use doesn't have an alignment rack so i have to go somewhere else. Will a shop adjust aftermarket control arms or just give you a print out and let you do it?
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Old 03-23-2018, 03:58 PM   #7
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Adjusting the CA's is not rocket science but is is some added work. Ask the 4x4 shop who they use for alignments.
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2014 JKUR, Leather and everything inside, 4 inch OME springs, all Alpine arms, Adams front driveshaft, Falcon 2.1's, Adj track bars front and rear, heavy bumpers and winch, ICON rims and 315-70-17 BFG KO2's, ARB diff covers, ProComp LED's, 2 Bernese Mtn dogs.
Previously 2001 XJ lifted 5, SYE, True-tracks F & R.
CJ7, 304V8, auto, loaded, Detroit rear, and more.
90 Bronco,, 76 Bronco,, 70 Bronco
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Old 03-24-2018, 12:28 PM   #8
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Originally Posted by Sicarii View Post
Thanks, I think that is what I will shoot for. I haven't had a jeep aligned at a shop before and the 4x4 shop I usually use doesn't have an alignment rack so i have to go somewhere else. Will a shop adjust aftermarket control arms or just give you a print out and let you do it?
You can do this yourself with an angle finder and a tape measure. Assume the Unlimited 44 has a 10 degree offset, which is pretty conventional for angle corrected housings. Set your caster at 4-5 degrees and you should be in the pocket with driveline angle.
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Old 04-09-2018, 03:09 PM
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Thought I would add the final result for this thread. I ended up going with Teraflex Alpine adjustable front control arms. I found a place to do an alignment, and everything is nice and in-spec now. Caster is at 4.8 degrees, everything seems to drive nicely except the steering stabilizer that Northridge put on (the DU44 has a different type of bracket, so it needed a new stabilizer) is gas pressurized and causes a slight pull to the left. I have to figure out a better replacement that doesn't cause a pull. I can't really complain, they didn't even charge a new stabilizer as a line item anyway. The shop I went to was happy to adjust the UCA's and the JKS track bar and only charged me the standard alignment fee of $79, which I feel is pretty good for what they did on it.

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