Hi all - looking under my (new to me) 2015 today I noticed a lot of slop / play in the stock front driveshaft.

I am not well versed on 4WD workings yet so I wanted to ask a few things:

- normal or no?

- if not, likely to be a u-joint issue or something else?

- lost my job so money is tight, but also have a 12-hour camp trip which WILL require 4x4 in a few weeks (been planning and promising my son this trip for almost 2 years after our last trip got cancelled). What are my options for fixing this with limited funds?


Info:

- 2015 Rubicon, 64k miles, 4" lift w 35s

Video:

Video of me pushing/pulling on driveshaft

 

The twisting action is simply the backlash in the ring and pinion gear setup which would typically be normal; however, you should not have that back and forth (in/out) movement at all and the sound is no bueno. I would guess crapped out bearings with possible damage to the gears. The DS is attached to the pinion flange which is bolted to the pinion gear (via the pinion nut). That pinion gear should be solid, and firmly held in place (with slight pinion preload) by the bearing and shim combination. That is not a good sign considering your situation.

 

If the bearing or gears have damage, what is the best course?

And what likely outcome would there be if using 4wd at all, for a limited time (maybe 15-30 minutes of fairly light total use for where we are going)?

Lastly will driving it in 2wd with the front DS still installed cause harm? Or is it ok if not under 4wd load?

I am somewhat mechanically able, though messing with the differential, axle, etc. has always intimidated me.

A few weeks after trading in for this JK (beginning of June) I noticed a small leak from the driver's side front axle, guessing the seal is blown. It probably needs replacing too.

 

Did that have factory gearing in it? I'm wondering if this issue already existed when you bought it and it just got progressively worse when you realized it. You're pretty much looking at a complete axle disassembly and likely entire regear. Keep in mind all the components are spinning inside the diff regardless of 2WD or 4WD, and regardless of front DS installed or not (ie, the tires are turning everything from the outside in). I'd suggest driving like that is going to resort to no 4WD pretty quickly. I'd think you're going to chew up gears pretty fast if you have not already, but that is just my opinion. You might drain the gear oil and pop that cover off and get eyeballs on the gears just to see what they look like. You'd just need some new RTV and a couple quarts of gear oil to put back in. Not what you want to hear, but I don't think I'd be going on that trip. If my diagnosis is right, you're likely looking around $750 for a front rebuild with new gears as a guestimate around this area.



Just so you can understand what's going on here look at this generic exploded view. You have the pinion gear (#2), then shims (#3) slide on to set the pinion depth, and then bearings (#4) are pressed on. The bearing race (the 2nd part of #4) is pounded up in the differential from the inside and are what the bearings ride on. The pinion is then pushed up through the axle. On the outside of the axle you have another bearing race that is driven into the axle, and another set of bearings (#6) that go over the pinion gear shaft that is sticking out, oil slinger, a pinion seal and either a yoke (pictured) or a flange follow and all that is held on tight with a pinion nut. So essentially you have bearings inside and bearings outside that are applying force towards each other and keeping "preload" set so that the pinion gear is not loose and contacts the ring gear evenly as everything rotates around inside. The whole thing could be explained in better terms but we're just going to laments terms here so you can understand why there should be no play like you are seeing.

 

Thanks for all of that!

- I'm sure whatever this problem is was already that way when I traded in for it in June (1500 miles ago). I haven't used 4wd at all yet other than putting it into 4wd for a minute the day I bought it to see if it worked.

- If it could be done for $750, I could possibly sell my guitars to pay for it. Sadly with the economy as it is guitars are selling for about 40% less than they were a year ago. But if it gets it fixed...

- I don't know if it has the stock 3.73 gears still or not. The previous owner replaced the differential COVERS but no idea if more was done or not.

All I did that is related is drain and refill both differentials with fresh gear oil the week I got it, just to be proactive. There were no metal shavings or pieces when I did.

 

I don’t really think the rotation is too far off of normal. The in/out movement coupled with the rattle sound makes me think that your pinion bearing is bad, that would cause some extra rotational play as well as a slight in/out that you have. That’s my guess. You said you didn’t see any metal when you changed your oil so I don’t think you have any gear issues (yet!). If you’re somewhat handy then you can disassemble your front axle, keep track of where the shims are for your carrier and the carrier mounts/orientation. Pull the pinion out, the crush sleeve may still be good. If you’re lucky, you can replace just the pinion bearing if that’s the cause. Reassemble everything by the book and you should be good. Do some research on pinion preload, that’s important.

You’ll need a press to do the pinion bearing or have a shop replace that alone. Since you have to replace the axle seals, the pinion really isn’t that much extra work.

edit: notice the pinion flange and end of the drive shaft looks wet, that seal is bad too which a bad pinion bearing causing a bad play in the pinion will definitely destroy that seal.

 

Here is another thought in regard to the upcoming trip. Right now with the jeep sitting on pavement the axle is stable and that front DS and pinion are not moving that much in that in/out manner. As you head offroad that axle is going to articulate more and the DS slip splines and poor pinion situation are going to be moving a lot more and you're going to have less consistent contact with the ring gear. Putting it under load of 4WD is going to escalate things .

 

That makes sense. Thanks for the input.

I sold one of my guitars online last night for just under $600 so that gives me a little to operate with.