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Unread 05-28-2015, 11:58 AM   #1
gpcl16
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1988 FSJ Wagoneer 
 
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U-Joint Angle Problems

I recently installed a 4" suspension lift on my otherwise stock '88 GW. After installation, I had a lot of wandering at highways speeds and lack of return to center at lower speeds. So I put in 4 degree shims under the leaf springs, bringing my caster to around 6 degrees, along with the proper toe alignment. The truck drives great now but I started getting a bad harmonic vibration (sound only, not feel) above about 50 MPH.

With the combination of the lift and the 4 degree shims, It looks like the angle of the front driveshaft where it meets the diff is fairly extreme. By my calculations about 10-12 degrees! I have the stock driveshaft with a double cardan on the T-case end and a standard U-joint on the diff end. My understudying is that the U-joint end must be near 0 degree angle with this style setup. Here is a picture of it:



I have removed the front driveshaft for the time being and the noise has entirely gone away, but I would like to figure out a solution for the problem. Not only is the sound annoying but I am sure it is putting undue stress on the whole driveline. The truck sees a lot of highway driving as well as off-road. It would be nice to keep the ability to run 4Hi at highway speeds but not really necessary. I am considering locking hubs. Obvisouly that would be a concern with the VC in my NP 229 but I am the only driver of the Jeep so I won't be shifting to 4wd without locking the hubs. I don't have the capability to cut the axle tubes and re-weld. Maybe adjustable ball joints to adjust caster instead of shims. (I actually need to replace a ball joint anyways.) Anyone with experience on adjustable ball joints? Maybe a different type of driveshaft? Any other recommendations? The truck is pretty much undrivable without extra caster so I can't just remove the shims.

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1988 Jeep Grand Wagoneer V-8
Dana 44s 3.31, Rear TrueTrac
4" BDS All-Suspension Lift
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Unread 05-28-2015, 12:15 PM   #2
CSP
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Unfortunately you're not going to be able to get anywhere close to 4 out of an adjustable ball joint.
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Unread 05-28-2015, 12:39 PM   #3
gpcl16
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How much camber adjustment can you get out of an adjustable ball joint? I need to adjust camber as well, though unrelated to this problem.
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Unread 05-28-2015, 01:43 PM   #4
Dngrs1
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I find this interesting because I have a 4" suspension lift on my J-10 and have never had any drivability or vibration issues. Front driveshaft is the same as yours and I am running QT. Maybe the drivability issues you are experiencing are a result of the worn ball joint and camber issues you speak of and not necessarily caster angle.
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Unread 05-28-2015, 04:23 PM   #5
gpcl16
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Quote:
Originally Posted by Dngrs1 View Post
I find this interesting because I have a 4" suspension lift on my J-10 and have never had any drivability or vibration issues. Front driveshaft is the same as yours and I am running QT. Maybe the drivability issues you are experiencing are a result of the worn ball joint and camber issues you speak of and not necessarily caster angle.
What year is your J-10? And how much of an angle do you have at the differential U-joint? I don't think this particular issue is related to the ball joint, though I can see how that certainly could cause a vibration. I have felt vibrations due to worn ball joints, tie-rods etc, and this is not like that at all. In this case, you can't really feel the vibration very much as hear it like a harmonic resonance of the pinion bearing or something. It sounds somewhat like a wheel bearing starting to go bad but is unaffected by turning or load decelerating etc. Purely wheel speed dependent. Also it is the same regardless of whether I'm in 2hi or 4hi. And with the driveshaft removed. No noise at all. And the truck drives great with the increased caster. No wander at 70+ MPH, much better return to center at low speed maneuvers, etc.

After I installed the lift, without shims at first, I drove it at highway speeds multiple times and had zero problems, other than the wandering due to lack of caster. I put it on the alignment rack to determine how much caster it needed, and set the toe etc. I had caster readings of 1.7 and 2.1 so I know it needed more caster. I drove it on the highway into the shop, dropped the springs down to bolt in the 4 degree shims and drove it out and boom, harmonic vibration above 50 MPH immediately.

My thought is that the extreme U-joint angle is causing the driveshaft to be out of balance and putting a lot of stress on the pinion bearing in the diff. Just wondering if anyone else has experienced this problem and how you solved it.
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Unread 05-29-2015, 06:00 AM   #6
RockRollin
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Have you measured the caster angle since the shim install? Are the u-joints (all front) fairly new? Have the tires been rotated since shims? (Wear pattern could cause described condition)
It does look like a lot of angle, but I have seen worse without harmonic vibration.
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Unread 05-29-2015, 12:24 PM   #7
gpcl16
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Thanks for the reply. I haven't remeasured the caster since adding the shims. I was at 2.1 and 1.7 before so I am assuming I am at 6.1 on the right and 5.7 on the left now with the 4 deg shims but cannot be sure without another alignment. I had free access to an alignment rack for a while but no longer working at that shop, so I'd have to pay for each alignment now. No point for me to align it again until I fix the ball joint. And I don't really like anyone else working on my vehicles.

I haven't tried rotating the tires but they are fairly new. Less than 5,000 miles on them and no unusual wear that I can see. I did rotate them several months ago before doing the lift. The U-joints are definitely old, so maybe I should start there. I do not feel any play in them at all, and I have greased them recently. But I can see how putting a different angle on an old U-joint that was running a near straight angle for so long could cause problems. Maybe the U-joint "wore into" running at a specific angle and now the load is being put on a different part of the needle bearings? I may as well just replace all 3 U-joints and go from there. I'll pick up some heavy duty Spicer U-joints. They are all 1310 correct?
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Unread 05-29-2015, 12:35 PM   #8
gpcl16
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Also looking at buying greaseable moog ball joint sets. Looks like the upper ball joint has an adjustable sleeve for camber, so I can get my camber dialed in as well. $85 for a set from BJs off road but a little cheaper from Rock auto.
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Dana 44s 3.31, Rear TrueTrac
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Unread 05-29-2015, 01:45 PM   #9
Dngrs1
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Quote:
Originally Posted by gpcl16 View Post
What year is your J-10? And how much of an angle do you have at the differential U-joint? I don't think this particular issue is related to the ball joint, though I can see how that certainly could cause a vibration. I have felt vibrations due to worn ball joints, tie-rods etc, and this is not like that at all. In this case, you can't really feel the vibration very much as hear it like a harmonic resonance of the pinion bearing or something. It sounds somewhat like a wheel bearing starting to go bad but is unaffected by turning or load decelerating etc. Purely wheel speed dependent. Also it is the same regardless of whether I'm in 2hi or 4hi. And with the driveshaft removed. No noise at all. And the truck drives great with the increased caster. No wander at 70+ MPH, much better return to center at low speed maneuvers, etc.

After I installed the lift, without shims at first, I drove it at highway speeds multiple times and had zero problems, other than the wandering due to lack of caster. I put it on the alignment rack to determine how much caster it needed, and set the toe etc. I had caster readings of 1.7 and 2.1 so I know it needed more caster. I drove it on the highway into the shop, dropped the springs down to bolt in the 4 degree shims and drove it out and boom, harmonic vibration above 50 MPH immediately.

My thought is that the extreme U-joint angle is causing the driveshaft to be out of balance and putting a lot of stress on the pinion bearing in the diff. Just wondering if anyone else has experienced this problem and how you solved it.
I should try to be clearer.
After the lift install, you experienced 'wandering' "due to lack of caster". I think the 'wandering' issue may have been due to the worn ball joints. You decided to add degree shims to correct the caster angle. I think you have created the vibration issue by adding degree shims.
I suggest you remove the degree shims and replace the old ball joints.
BTW, I think that trying to adjust front end alignment with worn suspension parts is a waste of time.
For what it's worth, My J-10 is a '77. I've never measured the caster angle.
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Unread 05-29-2015, 04:30 PM   #10
gpcl16
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Thanks for the advice. While I agree that the ball joint should certainly be replaced, I don't think that is the cause of my problems at the moment. I say that because right now the jeep drives perfectly with no noticeable looseness at all. And the steering wheel returns to center as it should, which it absolutely did not without the caster shims. So I can pretty much guarantee that it needed the correction to caster one way or another. 2 degrees is not enough caster for a jeep, let alone any vehicle at highway speeds. I can see how a bad ball joint could easily cause wandering, but that is not happening at the moment.

I don't think the ball joint would have much affect on caster either, mostly camber, which was a bit off (1.4 degrees on the left), but no adjustment possible with the stock ball joints so I left it as is of the time being. The wrong camber could cause uneven tire wearing and pulling but not wandering, as far as I understand it. And I do agree, there is no point to align without the bad ball joint being replaced. Unfortunately, I didn't notice the bad ball joint until after I did the alignment. I don't know if it just recently went bad, or I missed it somehow during the alignment. Anyways, I don't really have the time to do the ball joints at the moment, so I will likely have to sideline the jeep for a few weeks until time and money permits me to address the multiple problems. Thanks to everyone for the input and I will report back when I get a chance to do some repairs.
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Unread 05-29-2015, 05:35 PM   #11
RockRollin
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You can get a degree guage to spot check your caster, fairly cheap really. I recently replaced the u-joints on my KJ, not because I could feel play, but because I had an on throttle shudder, shudder gone.
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