Help me out of the rabbit hole (driveline issues)

[danredtj]

I'm deep in a rabbit hole trying to chase down a sudden nasty driveline noise that just showed up recently. I'm feeling pretty friggin beat down at this point and I'm almost to the point of just taking it to someone and telling them to fix it. I really don't want to do that. I'm hoping that I can do a brain dump here and some of you gurus can help me on where I go from here.

To level set, it's a 2005 TJ Rubicon 6-speed. Lifted 4.5" on 35s. UCF high clearance skid with lo-pro mount. 110k miles. I only drive it to and from (and on) the trails, it's not a daily.

On the way back from a trail in July I started noticing a nasty scraping noise when I let off the gas in gear. Sounded exactly like a bad bearing to me. It is very noticeable inside, sounds like it's in the middle (from to back and side-to-side), so transmission, transfer case, etc. It goes away if I put in the clutch. It goes away if I give it just a little gas (i.e. to be neither accelerating or coasting). No noise that I can hear on acceleration. Putting it in 4WD makes no difference.

My first thought from googling was "rear pinion bearing". I pulled the rear driveline and drove around in front wheel drive for a bit. Totally silent and butter smooth. That seemed to be the clear indication of rear pinion bearing failure. It also tells me that it's not the transmission, because I was starting to suspect my "No Stinking Good 370" could be the problem. But, quiet in front-wheel-only tells me it's not the transmission.

I was on the stock 4.10s so I "took the opportunity" to go get it re-geared to 5.13s, and have all the bearings replaced instead of digging through the stock gears to just replace the pinion bearing. I told the guy doing it about the noise. He said he'd check the wheel bearings while they were out as a result. After putting everything back together and doing a test drive, the noise was still there. He's a gear guy and remarked "yeah that's quite a noise" and indicated he thought it was probably transfer case (like, he checked that there was oil in it when he got back from the test drive).

So, I drove home with my new axle gears and horrific noise while coasting. I started to notice an increasingly loud squeak/chirp sort of noise.

I ordered a transfer case rebuild kit (from Novak, which didn't go well by the way, but that's a whole other story). Over the course of a couple weeks I went through the whole case. None of the bearings seemed like an obvious culprit, although they all did feel less good than the new ones, so I was hopeful.

After that ton of work, I put everything back together and went for a drive and there is no change to the noise. The scraping and chirping noises are still there, but I also got some pretty significant vibes now. I got back from this test drive and, well, let's say I sat in the Jeep in the garage for a bit.

I put the jeep back up with all four in the air and ran it in the garage. If I'm just spinning the wheels, I don't get any noise, going about 20MPH (in the air). However, if I give it some brake drag, I can reproduce the squeaking and the driveline vibes, and I think the beginnings of the scraping noise.

At this point, especially with the drive line vibes, I decided to drop the rear shaft again and go for another front-wheel-only drive to make sure I wasn't crazy, and also to hopefully show that my transfer case rebuild wasn't making things worse. Again, super smooth and no noise, but this time with less chain slack.

So here I am, hat in hand, looking for some help. I figure the only things left are:

1. Rear wheel bearings (they are original/stock as far as I know). I don't really understand why these would make noise only on coast, and only with the rear driveline in. The gear guy seemed to think they were okay, but maybe he "forgot to check", who knows. I could certainly go for some cro-mo shafts and new bearings (to match the front), but I don't really want to throw that money at them while I'm trying to determine the problem. If they *are* the problem I'd be more than happy to upgrade. Also doesn't seem like these would cause the vibes.

2. Rear driveshaft. This one is from Tom Woods about 8k miles (5 years) ago, which I put in when I did the lift. It feels totally fine to me on and off the vehicle, meaning I can't detect any rough spots or slack in the u-joints, the centering ball and CV yoke are all smooth and quiet as best I can tell. I can certainly rip it apart and replace everything, but I'm kinda skeptical that it would make these noises (but definitely starting to suspect it with the vibes).

What else could it be? Any other thoughts? Turn up the stereo and send it? Lubricate the wheel bearings with my tears?

(Edited to remove the vibes from the equation, since they were my own fault when reassembling things. See comment #7)

 

[CMBD]

Pinion angle?

 

[danredtj]

Yep, it's straight (i.e. zero degrees between the rear driveshaft and pinion). I also think that would have manifested as vibes first and eventually noise if ignored. It's a rubicon, so it's a CV rear driveshaft.

 

[macleanflood]

Throwout bearing although the driving with just the front driveshaft no noise thing kinda disproves that.

You're two hours north of me... getting closer to a functional shop but not there yet...

I've got an extra 231 with an AX-5 shaft in it...do you have a SYE? That would play into the pinion angle theory...

Maybe drop the skid plate with washers as a test?

-Mac

 

[danredtj]

To be clear, I've never had driveline vibes before I started trying to fix the underlying problem of of the scraping noise. So I assume my angles are all okay... The vibes are yet another problem that seems to be compounding the situation. I feel like I have to fix the vibes to get *back* to only the scraping/chirping noise, but I also don't want to lose sight of the original problem.

I just put the gopro under the jeep to record a video of the driveline:

In case you can't hear me talking, the first thing I said is "first gear idle", then I rev'd up a bit to a few MPH. Then shifted to second and said "second gear idle". Reved up to maybe 10-15MPH, then said "dragging the brake". I feel it in my butt with just the wheels spinning, but it becomes more noticeable with the brake.

No scraping or chirping noises this time, but I think things have to "warm up" a bit before they start happening. I don't normally notice them until I'm headed down the hill from my house, after which they're always reproducible.

From the look of the video, it almost seems like my rear output flange is wobbling a little bit? I dunno how that could be. I can't imagine how I could have put it back together in a way that would cause that. It also doesn't have any rock rash on it that would be indicative of me having smacked it on something. I don't look at spinning drive lines very much but I assume this wobble is not normal? Or am I just seeing things?

 

[danredtj]

Here's another view of the output flange up closer from the side and without the driveshaft:

That *can't* be normal, right? I imagine that's the source of the vibes, and I'd hope maybe related to the other noise issues in some way?

Surely I can't have caused something like that with the rebuild right? I mean, that is the back of the massive main shaft, which can't be bent, and I can't imagine that reinstalling a bearing incorrectly (or a bad bearing) could have caused something like that, right? And if so, I'd expect a lot more violence in the form of shaking and scoring and what not.

 

[danredtj]

Okay folks, vibes resolved! Sure enough, it was unrelated to the other problem. So, strike all the vibes-related content from the problem and I'm back to my original problem: scraping/squeaking bearing noise when coasting in gear. It's not the axle bearings, it's not the T-case bearings. I assume it's not the driveshaft now, so ... wheel bearings? Would they only make noise when coasting in gear like that?

BTW, the vibes problem was this, which I feel really stupid about since it's like the easiest part of the t-case rebuild and I was very careful. But, I guess if it can happen to Mr. Bransford it can happen to me.)

 

[danredtj]

Just for posterity, let me document the cause and solution.

The grinding noise seemed very (very) localized to the transfer case. Even the guy that did my gears said "well, if it's not the rear pinion bearing, it sounds like it's in the transfer case." I had checked the joints in the driveshaft many times and everything seemed tight and smooth. After ruling out the rear diff bearings and everything in the transfer case, I started to re-focus on the driveshaft.

Even though I've pumped grease in all the U-joints many times as a result of chasing this noise, I had missed that the centering ball also had a needle-type grease fitting. My front driveshaft (yoke type) has a non-greasable centering ball so I hadn't even considered that the rear one could be different. Well, the Tom Woods Rubicon flange CV socket (which holds the centering ball) DOES have a greasable joint.

So, I got the requisite needle and pumped some grease in there. It took a lot until it came out the seal. Once I did, the whole CV assembly became very loose. So loose that when I went out for a test drive I didn't even get past the end of the driveway because of the rattly, jerky, chunky feels from the driveshaft. So it seems like with no grease it was bound up enough to feel tight, but under the torque of coasting in gear, it would make a scraping and squeaking noise. Once I lubed it up it became really sloppy.

I called up Tom Woods and talked it through. They told me that lack of greasing that thing for 7k miles could have damaged it enough to cause those symptoms and that loosening with lube made sense. I sent it to them and they replaced the flange (because of the centering ball) and all the joints for good measure. After doing that, all is well. I will say they turned it around super quick for me and for a very reasonable price. I feel kinda dumb for spending so much time, effort and money when it was just the driveshaft, but...I had no way to replicate the sound on the lift so ruling things out was the only thing I could really do.

So, ladies and gents, if you have a greasable CV centering ball, grease that mofo good.

 

[AndyG]

Be thankful- a seized cv shaft will destroy the prized 241 transfer case typically.

Good job and good thread. Appreciate the follow up post. This type thread is valuable.