So I have been noticing this knocking noise coming from under the jeep. It only seems to do it when accelerating. So after reading some posts I figured I would take a look at the axle u-joints and also look at the drive shafts. While inspecting the rear drive shaft I noticed what looked to be dirt or rust on the underside above the rear drive shaft where it connects to the tcase. So I swiped my finger in it and it ended up being thick grease covered in dirt (see the 1st picture named "grease" - looks like a dark rectangle above the shaft). I took some other pics so I could see the top side of the shaft where it connects at the joint. Being that this is the first time in my life looking at a drive shaft I really don't know what one in good condition should look like. I keep reading about boots as well and really didn't notice any.



Anyhow, if someone wouldn't mind looking at the pics and let me know what they think, if I actually have something to be concerned about I would greatly appreciate it. Maybe it is an issue and perhaps the source of my knocking sound. But really I am wondering if I need to have something replaced. Fwiw, it's on a 2010 2-door Rubicon, 6-spd manual, with 4" skyjacker lift, riding on 37s.

Thanks!

 

More than likely, that's your problem right there. Taller lifts on 2doors means steep angles on the shafts. The little rubber boot inside that joint has been 'pinched', finally wore through, and is now spitting the grease out. Very common. If the joint is making noise, it is time to remove it and decide what to do. You can replace with another stock shaft, but with the lift height, the same thing will just keep happening to each new shaft. Or you can go to an aftermarket shaft that handles angles better. If you go this route, you will want to look at a set of rear upper arms as well so you can adjust the pinion.

To find out for sure if this is your problem, just remove the shaft, put it in 4wd and go for a drive. No noise, you found the culprit.

 

That's not a stock shaft. But I agree on removing the shaft, inspect, etc.

 

Funny enough, I was checking to see if I had adjustable rear upper control arms, (had to look it up first to find out what they were and where to look) and found that I do . And after reading another thread trying to figure out how to remove the rear ds and seeing what the stock one looks like, I realized the same thing about it not being stock.

Most of this work was already done before I purchased the jeep, so I am working diligently to try and figure out what I have and what I need. So now I am wondering what manufacturer is the rear ds?

 

I wasn't under the impression that a U-joint style driveshaft had inner seals? Unless I'm misreading something,

Personally I would so re-torque everything to spec to make sure you aren't getting vibrations from anything. But I definitely agree with checking the U-joint. See if there is a lot of play in it by wiggling it around. It may be time to replace the u-joint. It is also possible that you threw a weight off the driveshaft. Might want to have it rebalanced.

 

So, what would be the best option for new shaft or rather what options/details/features (e.g. double cardin joint) should I look at before deciding which to purchase?

Also, is removing and installing the rear ds pretty simple task?

 

Not sure how to test if there is play in the u-joint - but what I did (for the axles too) was try to wiggle them by hand. I got absolutely no play in them. Threw a weight off the ds - how do you test for that?

 

So what should I be looking for other than where the grease could be coming from?

 

My bad, I didn't pay attention to the pics. Just assumed it was the typical failure we see on the stock shafts.

So my guess will change to - lack of maintenance? If there are zerks on the shaft/joints/ball, grease them all up and see if you caught it early enough to save the joints. TF put together a good how-to vid:

https://www.jk-forum.com/forums/show...08#post2543308

 

It's very straightforward, take off the bolts spin it a little and it pops right out!