On a Mission: 50mph rumble

[SAString]

Since I've lost my cool, I went to Inland and left my KJ for them the inspect. I was suspicious because there were no weights, perhaps meaning no dead-nuts balance. They inspected and said they replaced my shaft with a stock length and mine is lifted (2" OME) so they "could have" made the wrong length for my set-up (does he know about the slip yoke?). Then he said, because it is lifted, the pinion angles are off, causing the vibration.... (a 2" lift?). They wanted $115 an hour for doing the measurements, then they would tell me how long it would take to add shims and make the corrections. AwwhhhhHHH!! JBA Y-Link extension here I come! OK, after spending $629 for the stock set-up and knowing I could have done a SYE and shaft for that price, will the Y-link and pinion angle adjust get rid of the 50MPH vibes???

 

[sota]

Do you, by perchance, have a set of stock wheels and tires you can toss on for testing?

 

[SAString]

Do you, by perchance, have a set of stock wheels and tires you can toss on for testing?

No stock tires available. Why do you ask? I had these vibes with the stock tires and wheels. I bought new tires and wheels plus had them precision balanced. No difference in the vibration frequency or speed which it occurs.

I'm feeling this through my seat, not the steering wheel.

 

[TomB985]

I’ve been following this thread, currently chasing a similar issue with mine. About to replace my front driveshaft again, I can’t get around the fact that it seems worse in 4WD for me.

 

[SAString]

I’ve been following this thread, currently chasing a similar issue with mine. About to replace my front driveshaft again, I can’t get around the fact that it seems worse in 4WD for me.

Hi Tom:

Welcome to the vibe club! Although you shouldn't be driving on pavement in 4wd going 50MPH! I'm driving without my front shaft now. I purchased a new one from A1 Auto and it went bad in about 1,000 miles. The rear CV joint next to the transfer case started to get rough and bind (maybe causing vibes) so after taking it out I took it to a mechanic that told me it was bad and get another under warranty, which I did but haven't installed it yet. Just trying to zero in on the cause so I'm focusing on the rear for now. Lots of people starting to direct me towards bearings....Yikes!

 

[TomB985]

Hi Tom:

Welcome to the vibe club!

Thanks! I hear it’s quite the exclusive group.

Although you shouldn't be driving on pavement in 4wd going 50MPH!

My KJ has the full-time transfer case, which many engage and leave in full-time 4WD all winter long. Haven't needed it yet for traction, but being able to use it on dry roads is great to help track down the issue (or lead me on a wild goose chase).

I bought mine with a bad rearward CV joints that had a completely torn boot. I started replacing the just the joint, which fixed the ratcheting sounded low-speed but I still have the rumble. Next was a complete replacement front driveshaft after the retailer will respond to my warranty request for the joint. That’s what I get for being frustrated and replacing the whole shaft; the joke was on me because the problem persists.

Lots of people starting to direct me towards bearings....Yikes!

The noise is fast enough that I don’t think it’s on the “slow” side of the driveline. That leaves something the transfer case or pinion bearings, front or rear. I don’t understand bearings, though… It only happens at certain speeds for me, and none of it sounds like a grinding bearing noise. Just a vibrating rumble.

My next action is to put it on jack stands have somebody run up the driveline to 70 mph while I get under with a stethoscope and try and isolate the noise.

 

[TomB985]

I think I found it.

At 65 MPH I'm getting a steady rumble from the right rear wheel bearing. All other bearings underneath sound identical to their counterparts. I had my assistant drop the speed to 30 MPH and it sounded fine. I've never had a wheel bearing act like this before, but it would certainly explain the problem I've been chasing.

Might be worth pulling your axleshafts and taking a look. I'll be taking mine apart this weekend. Not a big job by any stretch, but you need a slide hammer to get the old bearings out.

 

[SAString]

Hey Tom! How did the Right rear wheel bearing replacement go? Every time I think I figured it out, I spend a bunch of money on parts and blow a weekend working on it. Then, It still vibrates! Interestingly, it only happens when under load around 50 (tap the gas=vibe). Is yours the same?

 

[TomB985]

Looks like I completely forgot to update this thread.

I replaced both rear wheel bearings, and was surprised to see how good the bearing surfaces looked when I had it apart. As I suspected, no improvement upon reassembly A friend of mine has been a mechanic for years, and thinks it's probably carrier bearings. Apparently they can echo quite loudly through the axle tubes, which would explain why my stethoscope lied to me.

I'm done sinking money into this thing. It could go another hundred thousand miles with the rumbling noise, but I am far too **** to just live with it. I'm also currently pending a transfer at work, and I'll be driving a lot more miles, so I have already purchased its replacement which gets much better fuel economy. My neighbor is buying the Liberty in the next two weeks, if it gives her issues I'll help her with the repair.

 

[ltd02]

Okay may have to count me into this exclusive club. I have been having a mild rumbling issue under load in 2wd for a while. Mine starts around 40-45 and stops above 65mph. Usually pretty mild, but today, after using full time for some sub 50mph driving due to snow, I realized that the vibe or rumble I've always had in full time under load feels very similar to the rumble in 2wd mentioned above. Seemed way more noticeable after switching back to 2wd. Front driveshaft ends are fine as of about 30 days ago. I hope to pull the front driveshaft soon but after the 6" of snow today I may wait a bit...

BTW tires just rotated last week.

 

[SAString]

Okay may have to count me into this exclusive club. I have been having a mild rumbling issue under load in 2wd for a while. Mine starts around 40-45 and stops above 65mph. Usually pretty mild, but today, after using full time for some sub 50mph driving due to snow, I realized that the vibe or rumble I've always had in full time under load feels very similar to the rumble in 2wd mentioned above. Seemed way more noticeable after switching back to 2wd. Front driveshaft ends are fine as of about 30 days ago. I hope to pull the front driveshaft soon but after the 6" of snow today I may wait a bit...

BTW tires just rotated last week.

Welcome to the club! I am amazed how many people have this issue, on multiple pages and forums, and no one has discovered and provided a solution. Lots of money, experiments and effort, but no solution. I know there are lots of things it could be. I've heard it all and replaced it all, ending with the same exact vibration. If you are **** like me, this will drive you to drinkin'. Now I'm heading into unfamiliar territory of differentials and NP231J Transfer Cases. I've paid to have it analysed and all they can say is that it's in the driveline.....Duh.... Best of luck and please let us know what you find along the way.

 

[ltd02]

Following your issue has me worried but I'm hoping its related to the front driveshaft at this point. That's easy enough to test by removal. Suspect a bad CV even though the boots are OK. I've owned it for two years now and only remember it doing this for about a year now. Smooth when I got it but very low mileage and very clean all over.

 

[ltd02]

Well, mine's not the front driveshaft. If it gets worse I'll try the rear U-joints. Only 67k on mine...

 

[tommudd]

Well, mine's not the front driveshaft. If it gets worse I'll try the rear U-joints. Only 67k on mine...

Years ago I changed some rear u-joints on a KJ with 55,000 miles, rear one was almost rusted solid

 

[ltd02]

Years ago I changed some rear u-joints on a KJ with 55,000 miles, rear one was almost rusted solid

They do "look" good and feel tight for whatever that's worth but guess I need to see if they get hot after driving. Doesn't seem to be any noise but I don't hear all that well anyway.

 

[TomB985]

They do "look" good and feel tight for whatever that's worth but guess I need to see if they get hot after driving. Doesn't seem to be any noise but I don't hear all that well anyway.

The only way to truly diagnose a U-joint is to remove the shaft in feel for binding and play. You would think a failed joint would get hot, but that is not always the case. It's only a five-minute job to remove the shaft, just four bolts at the rear flange and removing one of the boot clamps at the front.

 

[duderz7]

Mine felt tight until I got the rear wheels off the ground relieving any tension at which point they showed thier sloppiness

 

[ltd02]

Thanks, I'll probably get to take a closer look at it this weekend. Maybe get it off the ground and see if there is any slop before I remove it. It's not terrible or anything, just annoying.

 

[SAString]

I just completed the JBA Y-link Extension installation. The test drive was inconclusive. Maybe a slight seat-of-the-pants improvement in the vibration, but it's still there at 50mph.

 

[tommudd]

I just completed the JBA Y-link Extension installation. The test drive was inconclusive. Maybe a slight seat-of-the-pants improvement in the vibration, but it's still there at 50mph.

Have you tried it without the wheel spacers ?
You do know that any slight amount of off balance could be it