harleymhs

Hey Guys, we have a 14 Polar JKU... Owned it from new... We had an issue with the rear spider gears and a noise , so the dealer installed a new rear diff unit in 2 weeks ago.. It was a new diff from Mopar.. All they had to do is take the axles out from the old one and install the diff... Since the day we picked it up after being there for a month... We heard a thumping noise brought it back the next day and they told me it was a flat spot on the right front tire, so after 51K we put a new set of rubber on the JKU.. Now still hear a thumping vibe in the rear on take off from a light ( doesnt happen all the time ) and noticed the same thing issue when coming to a stop.. Brought it back in to the dealer and the tech felt it ... Said it may be the pinion... Anyone of ever hear of a new diff having an issue like this? I thought it was maybe the rear drive shaft he said no.. Now who knows what Mopar will do , I don't want anyone rebuilding a NEW rear diff.. Any thoughts would be helpful... Thanks! We do have the MAX CARE warranty...

murdoc319

It’s never what I think it is, but the pinion could make a noise like that on braking- if the tech said he thought that might be it they could be right. The only way that would happen is if someone touched it- did they say anything about adjusting pinion depth? If they did, it’s possible they didn’t preload it correctly. Can you put the Jeep on stands and video it? You may be able to isolate it with the help of a friend

once you reproduce it, It will be either visible from the outside of the axle (pinion, axle, etc) or its on the inside. Using a mechanics stethoscope can help you determine where it’s coming from if it’s from the inside.

if everything is covered under warranty- id keep hassling them until your satisfied- it’s a pain but at least you’re not paying for it

harleymhs

No one messed with the pinion, came from Mopar Parts complete. We are dropping it off Tues for them to see whats going on. I'm hoping they remove the cover and see the issue or tell their rep need a new diff , or maybe better if they rebuild it the right way.... Who knows if the 2nd diff would come in and be the same or worse. At least if they rebuild it at the dealer they know its done correctly. Thanks for your reply.. No one can tell me if the NEW diff was a rebuilt or NEW .. The service writer told me they didn't core the old one its going to scrap that tells me its new...

resharp001

Maybe there is some confusion to how this all works, but the rear "diff" is not a once piece, already assembled, thing. There is no way they replaced the entire rear axle with new carrier and gear assembly which is the one way it would be something that was replaced without the pinion being touched. I'd suspect they opened the diff, pulled the carrier out, and replaced the spider gears inside. OR, they replaced the whole carrier assembly, at which point they are bolting a new ring gear to it and essentially performing an entire re-gear procedure, at which point they are reshimming the pinion and carrier for proper pinion depth, backlash, and both pinion and carrier bearing pre-load. So yes, they could jack a pinion up just as good as any cheap shop out there. Either way, it should be covered under warranty and you should let them fix it.

harleymhs

Def wrong answer! I saw the diff come in on a pallet! The ONLY thing they had to swap was the 2 rear axles! They diff cover was NEVER opened and all they did was add the oil and additive and swap the rear axles onto the new DIFF assembly! Look on Mopars parts site and you will see this is a COMPLETE rear diff!

murdoc319

Well you’re both right, sort’ve. First, resharp knows his stuff- he’s a JK Jedi for a reason and what he said was correct. However, you were also correct when you said the replacement part came as one piece and that the diff was replaced- it just wasn’t just the diff, it was the whole rear axle housing.

We were all a little confused around terminology. The differential is just the middle piece of the axle housing that connects the driveshaft to the axle shafts by housing the carrier with spider gears, ring gear, and pinion gear. It can be separated from the axle tubes but that’s a lot of work that’s not necessary. As resharp said, what they had to do was open then diff cover / drain it, pull the axle shafts with wheel hubs, pull the carrier, replace the spider gears, and reassemble. That’s a lot of work, and something else in there may have been wrong, so they just installed an entire new axle housing- which personally blows my mind. The spider gears are probably 100 bucks or less- haven’t looked, while the axle is a 5 hour job. Maybe they would’ve replaced the axle seals and whatever else but it’s still a lot cheaper than the 2k axle alone.

personally it sounds like the shop isn’t comfortable with gearing so they avoided it. That worries me because no one checked your gear alignment and they just assumed it’s straight from the factory- I’m sure it is but nobody knows. You must have quite the warranty to replace all that for free.

resharp001

Before you go tell me that I gave you the wrong answer dude, learn WTF a "diff" is. You got an entire axle assembly. Also, the "axles" they swapped over, those are "axles shafts". Best of luck with your repair.


I also can't believe a deal replaced an entire axle assembly due to blown spider gears. What idiots.

murdoc319

i know right?? That’s crazy!

harleymhs

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Who ever said the spider gears were blown?

harleymhs

thanks DUDE!