Hi all,


Looking for some guidance. Fairly new to the Jeep world. Just got my first Jeep (2012 JK 2 dr) 6 months ago w/ 93K miles. I've noticed a leak on my rear diff about 2 months ago which I then resealed with RTV and replaced the diff oil. It has been a month or so but yesterday I just noticed fluid coming from the diff area again and oil drops on the floor. The bottom of the diff is wet and towards to middle of the undercarriage. It was my first time using RTV or changing the Diff oil so I'm not sure I did some thing wrong. I smelled the fluid and wasn't sure if it was diff (which is strange cause diff oil stinks bad) Also, I noticed the body of the jeep seems to have a wet substance to it . Do you think I resealed it wrong or that the leak is coming from somewhere else? What are your thoughts on the cause of the leak? I've attached photos too.


Would like to know if this is something I can fix or take it to a shop. I don't mind doing the work but I am a noob.


Thank for your help!!

 

It looks to me as though your pinion seal is leaking. It's coming from up there by your driveshaft and then making it's way down to the diff cover before dropping to the floor. That looks like a pretty good leak if you're getting drips to the floor.

What you might do is clean it really good with a degreaser, dry it up, and then monitor after a drive or two. The leak will start to show itself quickly again, and you'll easily see if it's coming from up there at the pinion seal.

 

Hey, Thanks for the help! It looks like a pretty straight forward job to replace the seal. How about the oil / greasy film on the undercarriage of the body (shown in the 6th an 7th pic). Can that be diff oil also? or maybe it's some sort of rust prevention fluid (that's just a guess)?

 

It's really hard to tell on that 6th and 7th pic, but given you are in the northeast, that looks more like an undercoating of some sort....maybe old Fluid Film? That definitely doesn't look like something slug up from the jeep, but I don't live in your climate so I'm less familiar with what people do up there and what it looks like. The only thing is when I consider that to be some sort of coating, why is it not everywhere else? Maybe the jeep was degreased prior to sale?

A new pinion seal doesn't cost much at all; however, the job is never as fun and easy as we'd like it to be. You're gonna have to remove the DS and sometimes getting it out of the flange can be a pain. Then you have to remove the pinion nut which means opportunity to F up your pinion preload, but there's no other way around it. Then a lot of times getting that flange off the splines is fun.

 

Thanks for all your the help in clearing things up. Will do research on how to do the seal swap and get it done soon. I still have a lot to learn and lots of upgrades to do but loving the Jeep and the Jeep community!

 

You don't just pull it out and install the new one. You need a torque wrench that can measure the preload torque at the pinion nut.

This one will not work because it can't be used to measure torque ...
https://www.harborfreight.com/14-in-...RoCUssQAvD_BwE

This one will work because it can measure torque ...
https://www.autozone.com/wrenches-pl...E&gclsrc=aw.ds

 

Thanks for the tip. I was looking at videos on the install and see some who mark the nut and count how many treads are exposed to set the torque on the nut the same. Would that work also?

 

I'll be running a similar route shortly- installing new gears and I'll have to replace that seal. I've heard to do bearing grease on the back side and based on my experience with inner axle seal replacement with a dealer tech, I think I'm going to do RTV around the lip where it fits into the snout of the housing.

 

Probably get a few differing opinions, but here's mine. You're never going to be able to get accurate pinion bearing preload with any instrument unless you remove the axle shafts and carrier so there is no resistance on the pinion when you're turning it via the nut.

This is one of those things that most people will do a best-efforts thing, like counting threads and nut rotations, and throw some salt over their shoulder. All the driveshaft replacement instructions will say when you swap a yoke on (same process here) to just tighten that nut back to 160 ft lbs, and throw some salt over your shoulder the same way. You are so very unlikely to overtighten and compress the crush sleeve any more than it already is.....it would take a lot of torque to do so. You just want to make sure you don't get the nut looser than it currently is. I'd mark the nut and pinion with a paint pen, count the threads and the rotations to get the bolt off, and when you put it back on get it to the paint mark and just a smidge more. In a perfect world you'd never touch that bolt after the gearing has been set, but we don't live in a perfect world. This is why I mentioned even though it seems like a simple job, it will be more fun than you imagine.

 

Correct- preload will be .....15 in/lbs more than standard spec with the carrier installed. You're supposed to take a reading with just the pinion and then again with the carrier installed.

As Russ mentioned though- most folks will hammer off the old yoke and seal, slap a new one in, put RTV on the splines of the yoke, and zip it back together as best as they can get it. I imagine the failures come from folks trying to get torque on that nut with a 3/8" drive instead of using 1/2" and really ensuring it's seated back to where it was.