I've done a little research on this but no straight answers. First off backround: I have an 04 Overland with 155,000 miles that I've added Upcountry Springs, Rusty's 2" BB, JK Rubicon shocks modded to fit, and I'm running JK Rubicon wheels and tires (32" BFG Mud's on 17" Moabs). I recently replaced the front ball joints in the axle C's and after that I noticed a lot of wandering and flighty steering. Especially on the highway. I looked up front and found out that my stock tie rod was bent inward. So I added a JKS HD tie rod with Moog ends up front along with a stock 2012 JK Steering stabilizer that I got for free. I did the best I could to manually align my toe in my garage. I also replaced the track bar with a JKS track bar with Kevin's Offroad heavy duty bushings and aligned the track. This tightened up the front end a lot but I still have slight wandering at highway speeds but now I've noticed a noise that has been getting worse and that is this high pitch whining coming from the front from what sounds like the differential. Fluids were flushed within the past 9 months and yes friction modifier was added. This noise can be heard as low as 15mph as a sort of low pitch grind and turns to a high pitch whine when at freeway speeds. What makes me think this has to do with pinion angle is that when I try to slow the vehicle at 55mph by shifting it into 2nd gear (which adds a lot of down speed torque) the noise miraculously goes away. This however does not happen when just stepping on the brake. I have since ordered some adjustable upper control arms along with what I think are the correct bushings on the axle ends for the uppers. I'm hoping this cures the problem by adjusting pinion angle but does anyone think I've damaged anything else up front that is causing the noise? Carrier bearings? U Joint? (FYI the front U joint was replaced within the last 9 months also and before this noise was present)
I have almost the same issue. The only additional symptom I have is leaking gear oil out of my pass side axle tube. I have replaced diff oil seals, wheel bearings, cv axles and even done a DS swap replacing both yokes with IRO. Noise still present. Since the noise was present prior to my lift I am not directly associating it with lift and/or pinion angle. From my research I can only conclude the noise is also causing vibration which is causing my oil seal weeping. Since the noise gets louder with speed i am thinking bearings. I am of the thinking It has to be pinion or carrier bearings. With a big hunch toward pinion since when I did my yoke swap my pinion seal was completely rotten I would not be surprised if over time it was allowing my bearings to be contaminated over time without even realizing it.
Just my $0.02 I have not taken it to the mechanic yet. For a formal diagnosis but I am done throwing money at it for now.
Ok. I did that just now and drove it. Noise is gone. What does that mean? Just wrong pinion angle?
I'm assuming by your trim model and year that you have a conventional double cardan driveshaft. Verify this. Since the shaft is removed, check the ujoints, and the cv head for excessive movement/play. Once you determine the front shaft is OK, put it back in and see if the noise is still there or has lessened. If still there, measure your front pinion angle in relation to the front driveshaft angle. If the driveshaft is good, and the angles are good, then your noise may be in the pumpkin.