Daniel Kollars

Hello!
I am new to this forum, but have found many helpful discussions on here so I figured I would sign up and present my question/situation.

I have a 99' jeep Cherokee Sport with a lift kit. I have owned it for two years without any major issues I couldn't fix. I know very little about modifications and lift kits, so I'll just get right down to the issue;

Recently, I noticed a loud, metallic "bump" that would increase as I gave it gas until it would turn into a loud rumble/vibration (think of an old train accelerating from stop). Once I have any amount of speed established, the loud rumble/vibration only occurs when I hit the gas and stops as soon as I left off the gas. This is at any speed. I changed the rear drive shaft U-joint(one of the three, the one attached t the rear axle). I still had the same noise/rumble.
Next, I took off the rear drive shaft completely, put in 4WD part time(essentially turning it into 2WD front wheel drive) and took it for a spin, the sound and vibrations were completely gone! This leads me to believe it is something in my rear driveshaft causing the issue. I took it to multiple shops, but get turned away when I show them the "double U-joint" that is nearest to the front/transfer case. It appears to have a large metal ball inside of it, and I'm told only machinist will attempt repairing this type of joint. I called around, no machinist will touch it either.
So I decided to buy a new rear drive shaft, and now this is where it gets weird... I accidently ordered a FRONT driveshaft from carparts, but when it arrived in the mail, I noticed it matches almost exactly the rear drive shaft I am trying to replace. I thought, no big deal, maybe the front and rear are the same, it's worked for years for me without issue. But when I went to replace it, the one I ordered is not compatible with whatever type of SYE on the transfer case. My transfer case is the 242 model, but the part that attaches to my rear drive shaft looks unlike anything I could find online, and does not fit the new one I bought.
My old drive shaft attaches to my transfer case using 4 nuts/bolts. All the drive shafts I can find online attach to the transfer case with a yoke using U joint saddles.

So I would like to still replace the rear drive shaft, but I cannot find any that look compatible with my current transfer case set up. Any suggestions? Do I need to buy a different SYE completely?

Daniel Kollars

And yes, I know my original is missing a U-joint cap! I was in the middle of removing the U-joint on the old one when I noticed the problem...

Dave51

Why not just use the components from your old axle?

Or get this


What exactly is causing the vibration?

Is it only the universals?

Daniel Kollars

I was going to pull the flange yoke that would connect to my transfer case off of my old drive shaft and connect it to the new drive shaft I bought, the problem is the new drive shaft I bought is not compatible with the flange yoke, it needs a kind that has the universal joint saddles to connect.
I need the end of the new drive shaft to look similar to this: https://www.drivetrainamerica.com/sp...hoCr7cQAvD_BwE

I can't seem to find any rear drive shafts that have this kind of end, or have an open you joint that I can install this end onto. They all seem to only be compatible with this type of yoke: https://ruggedridge.com/p/rugged-rid...xoC2DcQAvD_BwE

Could I just purchase the slip yoke eliminator that I just shared above, to replace the current one that is on my transfer case? It seems like there are more options for this setup than the setup that I currently have.

As for where the noise exactly is coming from, all I've narrowed it down to is the rear drive shaft. I did replace the u-joint that is on the rear axle side, so I'm thinking all of my issues are in the double cardan joint, which no mechanic or machine shop around here will take apart and look at for me...

agreen

I've never dealt with an NP242, but from what I understand there isn't a SYE kit made for it unless you install a hack n' tap yoke. Of the 231 SYE kits I know of, the yokes are usually 32 spline. If yours still has a shortened stock output shaft, it's 27 spline.

I recommend unbolting that yoke and counting splines. If it's 27, order a 3103-27 yoke and cut it down as necessary to fit. Then you can use the more commonly available front xj driveshaft.

The real question, however, is have you opened the diff cover and looked in there yet? Are you sure it's the driveshaft making noise?

Daniel Kollars

No, I did not think about pulling the cover off the rear diff to see if that's where the noise was coming from, I guess I jumped to the conclusion that since I removed the rear drive shaft and the noise went away, that was where the sound was coming from. Now I will pull the cover off on the rear diff and see what it looks like though!

Are those double cardan joints really that hard to work on? Couldn't I at least just change the two universal joints in it without having to really take it apart? They are probably overdue to be changed anyways, and maybe it is just one of those u-joints gone bad that's causing my issues. The sound definitely sounds like it's coming from more of the rear underside. I drained the transfer case fluid and changed it, it looked fine did not see any metal particles or anything obvious. It seemed like I drained about the same amount it took to refill.
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agreen

If you have never pulled the rear differential cover, I highly recommend doing so. It's only going to cost you a few quarts of gear oil and some silicone.

As for rebuilding the shaft, it's actually fairly straightforward. Here's a video from BleepinJeep on how to do that.

ChuckQue

Give Adam's Driveshaft a call. They are solid and can likely point you in the right direction.

Daniel Kollars

I referenced the video that was shared, and decided to try to rebuild my current drive shaft. When we got it fully apart, the metal ball that sits between the two u joints was in a rough shape. We've rebuilt it with a new one plus two new universal joints. Put everything back together and it runs great, symptoms are gone! We also replaced the transmission mount while we were under there, it looked compressed and there was some play in the transmission while it was still attached, so not sure if it was the transmission mount, the rear drive shaft, or a combination of both when they were running together that caused the noise, but either way it is solved!

I did have to drive in four-wheel part-time to utilize the two front wheels to get to the shop and parts store though. I do now notice a clanking sound that starts slow and gets faster as speed increases but only when I'm turning or veering to the right. It sounds like it's coming from the front passenger side. When I'm driving straight though, I don't hear anything. Wondering if I messed something up in one of the front wheels driving it like I did. No vibrations or any steering issues noted, just the noise. either way, it's driving great so I'm not going to worry about it until I am forced to. Lol
Thank you all for all of your help!

Daniel Kollars

She's happy

Dave51

Probably the axle universal.

Get the sledge!

agreen

Excellent! I'm glad that video helped. If you plan on keeping that jeep for any period of time, watch BleepinJeep's channel. They've got some awesome tech on there, and most of it is geared towards the XJ.

Your front noise is (as was already stated) a U-joint. You already know how to do those, so get at it. Pulling the front axles can be a pain, but guess what!?? There's a youtube video for that too.

JMT

did you solve this problem with your rear driveshaft clunking under load by rebuilding the double cardan? When I remove the rear shaft it goes away. I can’t duplicate it on jack stands. I’ve been chasing it for over a month and think I’m going to go crazy. I moved on from the shaft since I sent it to Adams and they said it just needed the ujoint near the rear pinion, but reading your problem it sounds just like mine.