Well while you're digging around in the rear end doing wheel bearings, grab a magnetic stand and dial guage and check your backlash, look for abnormal wear on the ring gear and pinion. Anything obvious should stick out like a sore thumb. And these rear ends are a pita especially if they're not set up right. There's also the chance that one of your diff bearings are going.

 

You are rather fixated on that aren't you? I did look for abnormal wear on the ring / pinion when I was in there and one of the reasons I didn't pursue it any further was that there wasn't any. The diff fluid was low but not all that low, it was probably never serviced in the 167k miles but I can't say that with certainty. If the diff bearing was shot I would think it would have presented itself when I rotated the rear end while I had it opened, and it didn't.

I don't think I have a mag base for my dial gauge, I've only ever use it to set IP lift so that's not going to happen.

If I check now and it looks like there's a problem with a diff bearing I'm more likely to replace the axle assembly wholesale versus futz around with replacing multiple components; axle shafts, outer bearings/ seals / diff bearings etc. That would be signing up for a lengthy process that I'm not on board for. The 94 4x2 in the JY that I recently scavenged some parts from only has 113k mile on it, I would expect that the rear axle to be ok but I would have to look at it carefully before taking it.

Here's the fluid line in the old rear diff cover. It wasn't as low as I recall but it wasn't full and it also hadn't been opened up ever based on the rtv on the cover.



And the exterior of the cover, I really don't have any evidence that it had ever been off.



Steve

 

Just trying to help you cover all the bases. Just because you can't "feel" anything wrong when spinning it by hand doesn't mean there isn't.
On the other hand, I know it's a dumb idea but is your output yoke bent at all? Should be able to check it fairly easily. Chances of it getting bent without breaking or cracking are slim but it's something you could check in a couple mins.
Once again, just trying to help with some ideas, kinda what the forum is here for

 

I appreciate your suggestions even if it doesn't seem like my comment reflects that. It's been a very stubborn voyage and this project has ballooned into something I had never intended. After purchase I just kept finding more and more that needed fixing and this vibration has been the most annoying thing so far. And it's not even close to being over yet either.

However, I pulled the driveshaft today and took it in for balance check and there were a couple issues with it. If I remember what the guy at the shop counter said they consider anything at or below 3 thousandths to be tolerable. The center section was the worst at 25 thousandths, the front at the trans was 7 thousandths and at the pinion yoke it was 1 thousandth deviation.

To anyone who suggested this I apologize for dismissing it. I just have trouble accepting that a physical object can change like this but the shop owner said this is typical for Dodge and that it can occur because of torque and other forces. I just don't see how that actually happens, especially with a V6 engine, but I will accept that it can now after it's born out.

At any rate 95% of the vibration is gone and driving is much more agreeable. There is still some vibration at around 70mph that I will attempt to resolve but am not going to dwell on it at the moment. I took a video of the noise at the rear axle today and sent it to a friend for his comment and he seems to think that the rear axle bearings might be shot. That hasn't been confirmed yet but at some point I will go back into the rear end and pull the axles to check the bearings. For the present however I need to concentrate on getting the interior reinstalled and the water leaks sealed up.

Thanks guys!

Steve

 

I can replace all the bearings and seals in the rear end cheaper than getting a replacement from a JY. especially since the local U pull went away. I loved 1/2 price day there back in the day. (that was Tuesday)
When I went thru my 96 looking for a noise/ rumble, I pulled both front and rear diffs apart and was surprised at what I saw when I got into the bearings. (it wasn't good) but just by pulling the cover and looking around and spinning the yoke in my hand, everything "looked" fine. As long as you pay attention to existing shims location and amount and put the SAME AMOUNT IN THE SAME PLACES and you aren't replacing ring and pinion, you should be alright to open it up. To buy a kit though I have never found a diff kit that comes with axle bearings or axle seals, I have always had to get those separate.
I took advantage of opening up the rear to add a brand new Trak Lok while I was in there on that truck. (I had it on the shelf that I had bought for something else years ago, that is no longer here)
though it was made easier doing this job, having a 2 post lift of my own.....
I did screw up my 1st diff rebuild about 15 years ago, that was on a Cherokee, because the races and shims fell out when I pulled the carrier and ring gear// and I didn't see where the shims came from, and put them in where I thought they went.... that was a Dana 35. but have done about a 1/2 dozen differentials since without issue.

 

Thanks for the encouragement Don, I might crack into it this winter if I can manage it, might not get back into the garage once it's out because of another car taking its place. Part of my reluctance to open it up is that I've never done one before. I've just never had to get into one before.

You never know what you're going to get with upull stuff but I have gotten very fortunate over the years. It's too bad though that the upull here cycles through vehicles so fast you can never count on seeing the same thing a week later. I pulled trans out of 94 Dak 4x2 last week because they were pulling the vehicles in that row and I didn't want to lose a 113k mile trans should my problem be with that component. Now however I wish I would have gotten more off that truck since it was a twin to mine, perhaps even the rear axle.

The upull here though, has stopped with 'special price' days so in the case of the rear axle I can actually find a full service yard who will supply one of equal mileage for less than upull. I have told them that their prices are not really all that competitive anymore but they don't seem to care very much. They're especially high on tire prices now, they think that used tires priced $10 less than new is a bargain, which it is not. IMO used tires, even the best, should be roughly half of new unless they're clearly within about 100 miles of having been put on. Perhaps I'm wrong about that but I'll buy new for what they're selling tires for.

At any rate I ordered axle bearings and seals (SKF and Timken IIRC) a few days ago just in case there is a rear end problem and I have to dig in. I will post up the video of the noise I experienced and let the group help diagnose what the problem might be back there. I'll post up the link when I have the video uploaded. I think I ordered a pinion seal too.

Thanks
Steve

 

Here's a link to the video where you can hear the axle noise. While this video doesn't show it the noise will vary with changes in rpm. I have that video but it's a lot larger so I didn't post that one.


Let me know what you think, I've already had one comment locally that thinks it's axle bearings. There's no audible whining from the rear end but I haven't driven it enough yet to really pick out other noises etc.

Steve

 

Well if you were anywhere close to me in Michigan I've got a complete low mileage rear end from a 91 2wd v6 that you could have for free as long as you came and oulled it off the frame. It's only got 100k on it. Drive it 50 miles to park it where it sits.

 

That's a generous offer even if it's a significant driving distance. And based on your comment you think there's something to this noise? It seems to be coming from the outboard area on both sides so I would assume axle bearings. When driving on the highway I get no whine of any kind that would typically tell me the rear end is worn out. I guess I should pull one of the axle shafts to see if there's actual damage to the axle itself.

Steve

 

If there is damage, as long as it's slight, they make "repair kit" bearing/seal combos that shift the bearings out a bit, putting them on unused metal.

SKF sells the R1559 ( https://www.rockauto.com/en/catalog/...t+bearing,1664 ); you also should use new C-clips at this age.

RwP