Wife's 2011 Escalade- 6.2 AWD. 258k.

About 3 weeks ago, it developed a vibration I could feel in the seat above 70mph. I also had some slop in the steering. I found out inner tie rods were shot, so replaced and had aligned. Front end has new outer tie rod ends, upper ball joints, passenger side power steering bushing. No change.

Following all that, I put new wheels/tires on to replace the OEM wheels, and figured with the age of the tires they were probably out of balance. New wheels and tires, balanced, no change.

Replaced both rear driveshaft U joints and the "easy"/front joint on the front driveshaft before heading for Texas/NCA. Ran low on MAP gas so I wasn't going to start melting plastic and not be able to finish the rear joint on front shaft- I'll do when I'm back next week and not pushing snow or freezing. The front shaft joints still felt tight and smooth. Not as bad, but still there.

Hubs and lower BJ's probably have 50k at most. Rear shocks are new Monroe air ride in the last 2 months/10k, and front struts (Delco) have about 50-60k.

Vibration- it's NOT consistent. It comes and goes depending on the road. On the way to TX, one road surface I kept it at 78 (painfully slow) and it was tolerable. Didn't feel like I was going to damage something. Same highway, road surface changes to newer or older, and I can go 82-83 and it will "feel" as intense as it did at 78. Another change in road surface and I can go 84+ before it feels like it did at 78, or I have to back down to 78. Feel it going downhill on the interstate more than flat sometimes, and uphill more than flat sometimes. Also seems to be slightly felt in the steering wheel, though it feels like it's directly under me or to the rear.

Stuck my head out the window Dumb and Dumber style at 75mph to see if the tires are bouncing, wheels look bent or canted. Looked good.

Lowering air pressure made it more tolerable.

Vibration is still there when I shift into neutral.

I noticed that the vibration wanes. It almost disappears, and comes back strong, wanes lighter.

Only noise is a LOW growl/rumble from about 70 up, regardless factory wheels or the new. No metallic noises.

Checked rear axle bearings and they seem fine. Pinion was solid- no play that I could find. Diff fluid for both diff's has 50k highway miles.

Downloaded a resonance app to try and pinpoint the RPM/frequency, but I'm not quite smart enough to figure out the Z,X, and Y axis in relation to how my phone sits.

Just realized forgot to check front pinion- I'll go when I do the last u joint.

What else could I be missing?

 

Front hubs?

 

Do you notice the waning changes as you go around sweep curves (front wheel speed differential)? If so, it could be the front differential. How did the fluid look when replaced 50K ago? Have you checked it since? The preload adjusters in the 8.25 IFS differentials are notorious for backing off and reeking havoc on the bearings, even worse on the AWD since there is always load thru the differential.

Another item I didn't see were checked are the front cv shafts.

 

Check to see if the brakes are dragging, esp fronts. Happened to my Av once. A wheel with that will be extra hot.

 

I'll check those. Had one freeze up on this truck years ago. Ugh.

No changes in curves or turns. From what I recall, fluid looked good for 100k fluid. I might change both out again if I have time this weekend. I'll check the front CV shafts tonight.

Both sides I could get a metallic "thunk" at 3/9 initially pushing both front of the tires/wheels into the center of the vehicle. It sounded like it was coming from the oil pan area though. Zero play at 12/6.

Checked and zero play aside from an initial 'thunk' mentioned above.

Replaced the last U joint Friday. Glad I didn't attempt with the MAP gas I had left- wasn't enough for 1 bearing cup. Also checked front pinion, lower BJ's, hubs and rear wheel bearings for slop with nothing being obvious for play.

New U joint eliminated the growl I was getting though it seemed really tight. I was also able to comfortably hold about 83/4 to Des Moines, but the vibration persisted- came and went and seemed more pronounced downhill. It also seemed to be more front end vs the whole truck now- sometimes you could see the steering wheel visibly shaking. Could still feel in the seat, but it's not as much as before.

I have to pull the steering rack this week/weekend to replace the 2 driver side bushings and install the other half/reinforcement of the poly kit. If that doesn't cure it, my next thought is the Z95 Magneride struts. After looking back at mileage logs (Installed Mid June of 23), the front struts (BWI) have about 80-90k, not 50 or 60k like I thought. I've heard the 22's really tear them up, and Magneride parts aren't exactly known for longevity.

 

I have never been able to diagnose a bad wheel bearing by looking for play in the wheel, they always felt ok. The only way that I found to be definitive is to remove the wheel, caliper, and rotor. Then turning by hand you can feel or hear a bad bearing. But I never worked on a 4WD, I don't know if the axle would need to be removed to feel a bad ***** rumbling in the bearing.

The easiest one that I diagnosed is when I had the noise for some time, and all of a sudden it gave out and my inputs to the steering wheel were like trying to tell a cow which way to turn using a cattle prod. Luckily I was only going about 25 mph and close to home.

 

Fortunately or unfortunately, I've always had 4x4 or AWD. Caught most of my bearings from noise and vibration that would get worse or go away based on the direction turning. I've become more suspect of the front passenger corner overall- checked the hub again for play last night second guessing myself since I initially did it with both tires off the ground- did just that tire this time. Had a couple I caught close to home like that. Somebody's watching over us...

I'll try checking in neutral for the spin test tonight.

Update from the last couple days:

- Brakes don't seem hot, or one side hotter than the other. Everything temped out similar/low enough for no dragging.

-Vibration coming on a little sooner 65-70 mph now. Still not consistent/patterned, and seems more intense going down hill. Feels more from passenger corner now.

-Our temps are swinging from 27* in the am to 70-80 in the afternoon. Vibration seems not as bad in the am, and worse in the pm.

-Found some slight leakage from the passenger front strut. Truck gets washed almost daily so it's usually pretty clean underneath.

-Bounce tested the front (best I could without a real front bumper and all 190# of me). Drivers corner seems tight, passenger loose/bouncy.

That being said, I'm suspect of the struts even more so than before. I ordered some Arnott SK2954 passive loaded struts yesterday, should be here Friday. Also found a NIB/spare SKF hub in my garage cupboards, so at least I'm prepared should it fail the spin test tonight.

 

Spin tested both front hubs last night. Felt great. No noises.

 

Good evening. Friday update.

Swapped in Arnott loaded struts. Rides soooo much better. Lifted front end, but new springs. no miles. Drove to dinner in town down the road. Got her up to 71. Vibration still there @#%^#@#. Didn't arise until about mile 2.

Wife said she thought it was coming from her side, confirming passenger front. All that's left to replace that rotates is hub and cv shaft. . Doing the CV shaft. Felt tight, no noise when I checked it but screw it. Just ordered one from Advance since I can grab and install tomorrow a.m. Hate 'throwing parts' at this, but to the point of getting sick of it and wanting to dump the truck. Enjoy sleeping in bed too much, and she doesn't like diesels.

Going to measure inner hub bores on wheels for hubcentric rings as a precaution, and change diff fluids too. It's due.

 

Another update. Bought and didn't install the cv axle. It will work on this truck or our procharged sierra, so spare for when it's needed. Checked the CV's again, loaded and hanging, and zero play.

Replaced the rack and pinion bushings, and installed the reinforcement that came with the poly bushing kit. Side note- bushings can be done with a ball joint press kit, but you'll need several adapters not included in the 'smaller' kits and you'll need to get creative, as well as have an air hammer handy. Unfortunately, this didn't fix the problem but made steering even more responsive.

Drained and refilled the front diff. Might have found the problem- @BigKID might be onto something. I still haven't exhibited any symptoms getting better or worse turning, sweeping turns, etc. Appearance was antisieze/finely ground forbidden glitter, followed by normal looking oil. Magnet had a few slivers and antisieze slime on it equalling the diameter of the bolt...amount that came out seemed low, but no leaks so far after 100+ miles on her yesterday/today....

Since doing both of those yesterday, It's back to coming in at 78+, and so far not "hitting" as intense as previously. Going to add some Lucas to it today when I do the rear fluid between running girls to practices to see if that helps until I can replace. Going to see if I can get a front axle locally to swap in when everyone opens Monday.