1999 Jeep XJ Sport, Auto, 4WD part time, 4dr, 4.0L (Previous owner had changed the front end to a older one that used vacuum to slide a collar to lock it in)

In the last couple of days, I started hearing a noise that seemed to disappear at speeds above 40mph (or other noises are hiding it). It seems to be a metallic rattle but as you slow you can time it to a wheel turning or driveshaft.

So today, I pulled the front left wheel to start my diagnosis. I turned the front drive shaft and heard a metallic "clank", I disconnected the front driveshaft and grabbed the yoke on the differential and turned it quickly back and forth and the "clank" is coming from the differential

About a month ago, I had pulled the cover off that differential, modified it to lock the collar in 4WD and changed the fluid in it. That is about the only history on it I know.

So what is the consensus opinion on why it "clanks" and the remedy for it. I am still thinking a Dana 30 HP in the local JY. It would be a bit of work to pull it, no air tools, no jacks, etc but I am really thinking about giving it a go. That would put the XJ back on stock differentials.

 

I am by no means a diff expert, but upon removing the cover and a close visual and tactile inspection, the next thing I do is attach a magnetic base dial gauge, and measure the specified backlash on the gears, and also put pattern marking compound on the gears to see if the pattern is acceptable...if it fails those tests, it usually needs a rebuild

clunking could be a few things, but most of them would mean a rebuild (or replacement).

I am not familiar with the older style front axle, so perhaps you will be fortunate

 

What'd you use to do that with?

Pull the cover and post some pictures.

You don't need air tools to change out the front axle. And only one jack really.

 

I guess that part of my post was not clear, I actually opened the axle at the "vacuum assist housing" and pinned the locking collar over using parts I modified. This thread, https://www.cherokeeforum.com/f2/99-...-lines-258873/
has the pics. After I did that, I opened the pumpkin and drained and refilled it. I think you suggested a more intricate fix to locking the collar over. Sorry about the confusion in my post.

What I was referring to was "tools of comfort" in removing the junkyard front differential, with a saws all, air tools and a jack, it probably would be a 30 minute job..... Of course, no air tools or jacks in the junkyard, so I will load up heavy on tools and then I will just have to go back to my truck to retrieve them if I don't bring enough in. This yard has 1-2" sandstone rocks for a base, and makes for a less then comfortable work space.

With the clanking, I think it has a pinion gear bearing problem? Again the noise is hard to describe when driving, almost like something is rubbing to a metal to metal contact sound, then as you slow you hear it as a rubbing rotational sound.

 

Not me, Syracuse Dave, I missed that thread.

If you've been driving around on dry pavement in 4WD I'll bet you blew up the spiders. Pop the cover and take a looksee.

 

You are never going to know unless you pull the cover and have a look

 

I haven't, but I will. In other words, I haven't been driving around on dry pavement, but I will end up popping the cover and looking! I have already opened up the cover to the old "vacuum assisted collar" and nothing has changed there.
Right now, with the front drive shaft removed from the front differential, I can grab the yoke and by turning it left (about 1/2 inch) it will clank and turning it to the right (about 1/2 inch) it will clank. I think I dislike the PO, now. But I knew there was something different
about this XJ's front differential when I bought it so its on me. While digging around the under the front, I also observed where the exhaust pipe below the flange where it connects to the exhaust manifold has a dent in it resulting in a restriction of at least 1/2 the pipe.

I just have the feeling I am destined for the gravel of the junk yard.....

 

I don't disagree, but I might not even see what it is. One thing I have avoided in my mechanical experience is differentials, it is easier for me to replace this one with a junkyard one then try and replace the gears/pinion in the one I have.

But I will look and take a picture or two. After it is all said and done, I might get some experience on taking this differential apart. Makes me more of a "parts swapper" but whatever is easiest is the way I will go.......within $$ reason.

 

Kinda like this?




Credit ThunderThighs

 

Or maybe like this?



Credit Weamdreaver

 

Yep like that from the angle I was looking at it, so that's supposed to be like that?

 

there is a stock dent in the factory downpipe for clearance...restricts to 1-1/2" imo

bigger headers and exhaust make way more power, best power boost you can get, dont care if anyone thinks else whys

 

See

https://www.cherokeeforum.com/f2/den...162353/index2/

 

Well, I may have to look into getting my dent relieved....

Back to the clanging noise, I have thought this over and over and decided to look again at the vacuum collar that is on my front axle. Upon re checking it, the collar had shifted to the passenger side a little....could have been enough to be on the shoulder of holding/locking the split axle in sync. So I removed the fork, added a hose clamp to hold the collar over instead. Re-attached the front drive shaft and the clank I was hearing from the front differential was still there but after more thought it only clanked when it first engages. So, I took it for another test run and did not hear the aggravating whirring noise I was hearing before. Waited for the wife to get home and took her for a drive and she says she doesn't hear it any longer as well. (Her ears are better then mine!) I was telling her about the front axle was not original to the XJ and SHE suggested I might want to grab one from the junkyard. Like land, they ain't making XJ's anymore! Got tools loaded up in the XJ and will pull my trailer to the UPull yard to go for the heist tomorrow!

So it looks like I overlooked the most likely culprit.........the collar fork mod........I had done and now redid. With drive shaft attached, I don't even hear the clank when moving from drive to neutral to reverse. A short drive down the road is my 4WD testing grounds, I tried out 2WD, 4WD High and 4WD Low and they all performed as they should.

A big thank you to "Connecticut Dave" Dave51, awg and others who responded to my post for assistance! I need to quit overlooking the small stuff!

 

I'm wondering if a standard one piece axle would fit that diff and eliminate worrying about it in the future. Also the late model XJs had a LOW pinion front diff that everybody complains about. I only see that as a problem for extreme off-roading where you might ground the driveshaft on rocks.