I know many have followed the last round of very confusing vibration symptoms on Stinky, and now I can say why I couldn't sort it out quickly - there was a very long list of root causes. After changing some parts in the front, aligning it, and solving a sticky front hub, it drove smooth in 4WD in a snow storm, but not in 2WD on the dry highway. Apparently there are still two symptoms left to solve. They are easily identifiable and repeatable, and I have a question on each.

1. Vibration with speed from about 40-45 MPH on, and a continuous "raawrr-raawrr" that cycles every 6 seconds at 70 MPH. That tells me it's driveline related, no matter what the driveline guy argues. Do you concur? I couldn't spot this one before, because I haven't driven 70 MPH in a while.
2. There is a strong pulsing when I hit the brakes at highway speeds sometimes, and sometimes not. Is this the rear brake adding strain to a bad driveline, or is it possible the recent work up front disrupted my ABS system? After braking to a stop, I hopped out to thermo-check the disks - stone cold, so no dragging brakes or bad slide pins. I will monitor the ABS functions on my next drive.

 

In reference to #2, do you feel the strong pulsing in the brake pedal only, steering wheel only, both, or just in general?

 

Tire wear causes drive line stress in 4 wheel drive. Make sure front and rear tires a inflated to the same rolling diameter. Also check the front drive shaft closely. The double cardan joint can cause vibration and harmonics that can actually break the transfer case.

 

I feel them both when braking. All I feel when driving is that high-speed vibration, but it's nothing like what I was experiencing up until Friday - this is more subtle and easily identifiable. It kicks in at about 42 MPH, peaks between 60 and 65, and doesn't "harmonize" with the truck as badly at 70 MPH and up. I'll get Stinky up on the lift again, run him up to speed, and put a mechanic's stethoscope on it. I never got a chance to check the ABS, but that's coming.


Sorry bud, I screwed up - I omitted the feel and sound is in 2WD. That's being corrected in the first post.

 

New driveline shop. My small-town guy thought the driveline was a Douglas fir, adorning it with enough weights to make it look like a Christmas tree. The guys with the proper equipment gave the tree a shave and simplified the weights. Driveline vibration gone - now I need to find that last little brake-shaker if it pops its head up again. Stinky's crying "Uncle"!

 

Super! I am glad it is mostly resolved. On my old X, I had two front rotors that were ever so slightly warped. I am guessing that when they were both in some strange sync with each other, that is when the vibration and pulsing would happen when applying brakes. Sometimes it would not happen at all. Having the rotors turned solved the problem.


Also, recently I had one front brake line fail at a bad time. The weakness in them appears to be at the large diameter end of the protective boot about an inch inside. I am guessing that moisture gets in there and doesn't dissipate quickly and corrosion begins. Anyway, I felt a little pulsing, shimmying when braking for about a month before the failure. I attributed it to the above. I was incorrect! You can test yours by looking at them and if you see any rust where the rubber meets the steel then it may be a good idea to do PM and change them. I was able to lightly tug on the side that did not fail and it came apart in my hand. Just be sure to have the replacements handy or a second vehicle to get you to the parts store when you try this. They are about $23 apiece.

I was able to slip the two ends back together on the one that failed and it assisted in the limping to the parts house.. So, if you think about it, if there is the beginning of a slight leak/break in the line under the rubber boot, there could be just enough loss of pressure, due to hydraulic expansion and contraction under the rubber, to cause the ABS to sense it.

Just a couple of things to consider.....

 

That is exactly one theory I have. If they are just off-sync like a twin-engine boat or plane gets, you can hear the cyclic "rawr". The brakes make more sense, but I was thinking the driveline components would be involved: With lack of balance, a front U-joint under strain might "hum" with the carrier bearing. They spin at the exact same speed, but maybe a strange harmonic takes place - particularly with a rubber mount.


I'll check several points on the disk the next time I detect a noise or vibration - if it happens. This will help me find a hot region on the disk. The rear slide pins had the corrosion on the lower pins and I corrected that. I "assumed" that since the fronts were newer, I could put that off until I had more time. I think I'll change my priority on that, but I can't be sure the receiver end of the slide pin system won't revolt.

 

I have edited the above slightly... Be sure to check the brake lines....

 

I just wanted to add that Tugly was NOT loosing his mind with stinky's vibration issues. When I drove Stinky I could fill it in my feet yet subtle but noticeable. We took Stinky to a reputable drive shaft shop and was confirmed That Stinky's drive shaft was out of balanced and could have caused other issues in the drive train. With Tugly knowing his truck which is very important for longevity of the vehicle that he was able to detect this before other damage was done. Glad to know one more issue is blown out the tailpipe.