Regeared a 2007 Rubicon about 3,000 miles ago with 5.13. I was just checking things over and notice I'm getting movement in the front pinion gear where it joins to the driveshaft now and I see a small amount of moisture that appears to have seeped from the seal. No parts were reused on the re-gearing and pinion preload was set at the recommended 20-40 in lbs.

I tried throwing a torque wrench on the pinion nut but I can't get enough range of motion on my back to get more than 200 ft lbs which does nothing. This project was originally done at my dad's shop 1400 miles away so tough for me to do in my garage now.

This is my first re-gearing so wanted thoughts from the experts here on what I should try to do next. I can grab the driveshaft at the flange and move it enough to get a knocking sound. I'm hoping for best case scenario that the pinion nut has somehow backed off a bit. I assume worst case is that the pinion bearings are shot. I hope not since I probably only have 100-150 miles in 4WD on them.

 

sounds like either the pinion nut backed off or the crush sleeve was never fully set (crushed) to begin with.

 

You're going to be able to twist any DS and create a knock as the pinion gear rotates from coast to drive on the ring gear teeth. It's just the backlash. Trying to tighten that pinion nut even more isn't the proper thing to do and not going to help the situation......and as you see, is a fruitless effort with a manual breaker bar on the garage floor. It sounds like the pinion seal is leaking which isn't a super sign, specially since you just had that done. There is almost zero chance the pinion nut backed off.....that sucker is on there solid when it goes back on.

Not sure what to tell ya here. I think I would clean the rear of the diff very well, monitor for a leak through that seal. If it's leaking, I'd replace the seal and continue to monitor. If it's STILL leaking.....you're looking at tearing that entire thing apart.

 

As stated, rotating the drive back and forth will create a "knocking" sound as that's the back lash. The bask lash is important as you know to allow for heat expansion, proper gear tooth contact, and lubrication. Diffs are pretty dang tuff, I can't imagine a little bit of water damaging anything if noticed early.

 

If you are concerned, you could drop the diff cover and clean the parts and repaint the teeth on the ring gear and roll it through the pinion a few times. I know this is typically done without axles installed but seems it would work if the tires are off the ground.

 

A leaky pinion seal is not the end of the world, and is a common thing. It's not so common to fail 3k miles in though which is what kinda sux here.

Dirt Hammer - problem with trying to read gears again is leaky seal or possible pinion bearing issue is going to be related to pinion preload. You can get gears set up and meshing properly even if you have the wrong preload, so just because the gear pattern looks ok doesn't ensure there isn't an issue. Unfortunately, the only way to verify pinion preload is to break it all down.

 

I appreciate the comments folks. To clarify, what I'm feeling is not backlash. I can move the pinion gear up and down somewhere between 1/16" and 1/8" and create a knocking sound. The knocking sound is the flange hitting the inside of the differential housing I believe. The seal leak isn't my biggest concern although it is a bummer. It's not leaking enough to form drops. There is just a bit of visible moisture on the bottom of the differential but not nearly enough to form a drip. I can live with it for a while. I'm quite certain I set the pinion gear preload to 35 in lbs. I'm not an expert but I would assume once the preload is set the crush washer has been crushed to spec as well, correct? We did the rear first and it still seems to be holding up fine. I agree with @resharp001 about the locking nut. With red loctite applied I can't see how it would back itself off but I hope that's all it is it. I want to avoid a full tear down if I can. My main concern is that I'm afraid there is too much up and down movement to use 4WD at this point without risk of damaging gears. I think I'll drain the fluid and take a look to see if there are any large metal shavings that would indicate damage. If I see that, then I'll know it's a rebuild. If not, maybe I'll go with trying to tighten the pinion nut more and see if that works. What do you guys think about that?

 

THAT is definitely NOT good. I do not think you're going to find any easy fix for this a la "tighten the pinion nut more". That is just going to be 100% guessing game. I think you're looking at a complete tear down. Curious to hear if @TheDirtman has an opinion here.

 

If I recall there is a bearing assembly that's pressed onto the pinion shaft right? The only way I could see the pinion gear having that much movement would be lack of pre-load and or an assembly issue with the pressed on bearing? The pinion nut sets the bearing pre-load and basically sets the shims which were used for pinion depth.

 

Maybe didn't get the crush sleeve crushed properly That's bout the last thing I can think of.