In need of a little drive shaft help

BubbleGumSam

BubbleGumSam

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Original poster
Joined
Jun 6, 2024
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3
Location
United States
Hey everyone! Long time reader but first time poster.

I love reading about everybody's Jeeps and what they've done with them! The amount of knowledge you all have is amazing and I've learned so much over the years. I've only worked on bikes up until owning this Jeep but it has been a blast learning how to fix and maintain it. Reading everyone's thoughts on issues has helped me with any problems I've had up until this point, so thank you.

I'm hoping somebody has had a similar issue and am open to all suggestions before I throw in the towel and send it to a shop.
I will post pictures and a video of the issue at the end but here's some background first:

Dana 44 swap and SYE installed mid/late Summer 2023, ordered my driveshaft (non-greaseable) and SYE kit through Tom Wood's and the install went great.
Then I had the Jeep re-geared to 4.56 by a local shop early Fall 2023. Followed their instructions and everything went smooth there as well.
Never noticed any sound and drove it until late November when I garaged it for Winter. While in the garage I installed a 1.25in body lift.
Brought it out from storage late March and immediately had a quiet grinding/clunking sound: found that one of the front driveshaft U-Joints were seized. Took the front drive shaft out
and the noise went away. (Front drive shaft is still out and awaiting new U-joints and centering ball).

Now for the problem:

While driving slowly next to a fence I heard a faint but rapid squeak that sounded like birds chirping. I lifted the rear axle and had it spinning in drive and sure enough it was coming from the rear drive shaft area. Odd since it has maybe a thousand miles on it, but I currently have 31s with a 3 speed auto and 4.56 gears, so it's spinning pretty fast. I read about angry sparrows and how it's usually caused by the centering ball in the double cardan joint being dry or worn.

So I filled the flat zerk on it with grease and reinstalled the shaft, same noise.
Replaced the centering ball and all three U-joints with new ones as the grease in all of the caps smelled a little burnt and was a black color, same noise. (The needles all looked perfect but figured I would replace them with new ones anyways to rule them out.)
I even put the front drive shaft centering ball unit on it just to check, identical noise.
Took the output yoke off the transfer case and put ATF on the the seal and reinstalled, same noise. (Output shaft bearing has oil in/on it and spins smoothly so I'm assuming the pump is working properly I think? Case makes no other noises.)

Is there any way for a shaft to be defective at all? Could it be the pump in the transfer case? It makes the noise when in drive, reverse, and in neutral rolling downhill, but I cannot replicate the noise with my hands and the case in neutral.

^ All of this is without the front drive shaft attached.

Thinking of positives: I've gotten pretty good at replacing U-joints. :) Before I crack open the case, send it in, or get a new drive shaft, I'd love to hear any input from you guys!

Attached are the driveshaft nub, and a video of the sound: https://vimeo.com/954556587?share=copy


IMG_0503.JPGIMG_0504.JPG
 
The OP did email me, and I just replied to the email. For the benefit of future readers and so that someone maybe smarter than me can weigh on my "measure the hertz" suggestion, I'll copy and paste my reply below.

"I can't isolate the noise you are talking about in the video, I just hear a bunch of noises, all of which sound normal to me.

Because you've greased the shaft and replaced all of the joints and the centering ball I think we can confidently rule out the drive shaft. I wouldn't think that it is coming from the transfer case either, as long as it is full of oil/fluid. All of the moving parts in the transfer case should be fully covered in oil and should not make a squeaking or chirping noise. To further isolate the transfer case you may want to remove the rear shaft entirely and then put the jeep in drive so that you can spin the output shaft of the transfer case without spinning the driveshaft. If it still makes noise and if that noise seems to be coming from the transfer case, maybe it's time to open up the case and see what's going on. If the noise goes away, maybe the noise is further downstream, in the differential or wheel bearings or something like that. It's tough to diagnose because everything that is moving could be making noise, lots of different things are moving. One other thing you might be able to do that could help you isolate things is to measure the frequency of the noise. I just found and downloaded an app on my phone called spectroid. It seems to measure sound frequency in hertz. I'm not smart enough to tell you how to use that information to determine RPMs but if you could isolate the frequency of the noise in RPM you could determine if the noise is upstream or downstream from the ring and pinion. This is because everything upstream is spinning faster. If you have 4:56 gears your drive shaft and transfer case will be spinning 4:56 times faster than the wheels and axles. But this also could be a complete red herring because I don't think you'd be able to isolate the noise that you're measuring. The phone app might pick up another noise instead, just like I did when listening to your video.

Another thing I just thought of, similar to removing the shaft to see if the noise is still there upstream from the shaft. You could remove the rear shaft then drive the jeep in 4 high. By doing this, you'd be rotating the rear wheels, axles, and differential. "
 
Hey Shawn I just saw your email as I got off work.
In the video at the end I did have the transfer case output spinning in drive without the driveshaft and no noise was present. (I was also wondering if it could be any number of bearings between the engine and transfer case but since it doesn't make the noise without the shaft I'm thinking they should all be fine but I will keep them in mind.)

One thing I didn't test was spinning the rear axle faster without the driveshaft attached. I can spin it by hand but that doesn't produce any sound. I always thought pinions make lower pitched noises but can't fully rule it out. Anyone have an idea on how to get that part spinning?

I'll take a look inside each wheel bearing and see if something doesn't look or feel right, the speed of the sound is the only thing pointing me more to the shaft/tcase/trans/engine side but you never know.
It's also interesting hearing about the pitch of the sound, as I had a few people listen to it and some could hear it fine and others could barely hear it, even in person, it's very high pitched.

Thanks for the input so far and I will copy this over to Shawn so he knows I saw it.
 
I don't hear anything in the video either. Have you checked your brakes? they can make a squeak, esp if you haven't driven it in a while. I only say that because if I understand the timeline correctly, this noise happened soon after a layup after winter?
 
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