[stangmata]

2005 Rubicon, manual, 4:88 gear, SOLID diff covers, 106K miles.

In October I had 4.88:1 gears installed in the jeep by a reputable shop. After 500 miles (over 2 months) of following the break-in procedures that I was provided, the rear end developed a low groan that turned into a whine so bad I thought my t-case had blown. The shop claimed that I didn't break in the gears correctly and that they were subjected to excessive heat. Regardless, the shop elected to replace the R&P on their dime.

I picked the Jeep up with it's newest set of gears and when I arrived home, it had puked a bit of gear oil which I wasn't concerned about because the rear diff may have been slightly over filled. The shop said they added approximately 2 qts to the rear diff. I have SOLID diff covers so they didn't want to accidentally over fill the diff.

Yesterday, after a 10 mile drive, the rear end of my Jeep was covered in diff fluid and it was pouring out of the diff vent. There is fluid all over the rear fender, the tailgate, and my tire. There was a puddle in the store parking lot.

Today I added a little fluid and used a home-made dipstick and estimate that the fluid level is at the bottom of the axle tube (give or take). I verified that the diff vent tube is clear and that the vent valve was free (I even removed the small white cap). After a 6 mile drive, the rear diff was once again puking diff fluid at a shocking rate. The fluid is cool if not cold to the touch. I temped the diff cover with an IR thermometer at 110 degrees.

The shop is baffled and if I can't diagnose it over the weekend, they are going to take the Jeep and try to diagnose the issue. I'm not sure what to look for next.

 

[rlenglish]

Break in procedures for differential gears is a way for manufactures to not stand behind their work. This might just be my personal rant, but think about it. They are solid steel parts that require a specific set up to function. If they needed a significant break in then they would need to be re-adjusted after break in.
I have personally done and seen may differential rebuilds and after the Mechanic road tests to confirm their work then they are good to go. Think about race cars, they don't go through a break in they just get abused from mile one.

You did nothing wrong. If they had excess heat it was because the backlash was set incorrect.

Onto your problem,
My first thought is that it has incorrect or poor quality fluid. If it is coming out of the vent then it is foaming. If your shop is at a loss get them to change brands.

 

[stangmata]

I had this same discussion with the shop. I've owned a few brand new cars and I've never needed to break in the differentials. However, Google "gear break in procedures" and you'll read a plethora of articles that address the procedures and the necessity of proper break-in...all of which I was far more conservative than what's recommended.

I read this on another forum:

This is usually more of a problem when aftermarket carriers (ARB, Detroit) are installed. They recommend cutting additional drain passages to allow the oil to drain out of the tubes. If you have a stock open carrier it shouldn't be a problem.

I do have an ARB....

 

[Al_S]

Do you still have the OEM rear locker or did you add an ARB?

 

[Al_S]

OK I see the question was answered while I was typing. I had the same issue with my ARB install. Installer failed to read ARB instructions about the drain slot.

 

[JEEPINKC]

If this is a new ARB install, I would assume the differential tube drains were not addressed.
The ARB instructions describe this exact issue will happen if you don’t do what they say.
The fluid fills the tubes and can’t get back down into the pumpkin and then starts pumping out of the vent.
I just installed my ARB a couple of months ago and per the instructions my tubes needed the extra clearance to the drainage passages.

 

[elff]

Subscribed.
I am curious about what is going on.

 

[JEEPINKC]

 

[stangmata]

Thanks! This all makes a lot of sense. However, after the first regear (with the ARB) the diff puked a little but nothing like this. If it were an ARB issue I think it would have happened the first time as well. Maybe something exacerbated the issue.

I'll call the shop to discuss!

 

[JEEPINKC]

It is possible that the new set up or shims are blocking more of the drain passages than the previous set up.
I am guessing the first set of gears didn’t get enough fluid on them during the break in period and this is why the failure occurred.
Just a guess but sounds plausible to me.

 

[stangmata]

You're all heroes.

The Jeep is back at the diff shop. I called and highlighted the ARB instructions and when I dropped the Jeep off they already knew what needed to be done. They're being very accommodating and professional, which I appreciate (mistakes happen). I'll provide an update once I have the Jeep back.

 

[elff]

That's awesome.
Like you said, mistakes happen, but it's how those mistakes are handled, that defines a business.

 

[stangmata]

They called today and from what I understand, the tubes had slots but they probably weren't big enough for gear oil. The shop enlarged the drainage passageways and the Jeep is no longer barfing diff fluid. They're going to keep the Jeep for another day and drive it some more tomorrow to ensure it's gtg before I pick it up (which I greatly appreciate).

As an aside, my ram decided to split it's radiator so I'm driving my son's Comanche around (no complaints there!)

 

[elff]

My Love reaction is for the Shop's work, and that commanche, not your unfortunate radiator issue

Got any Pics?

 

[katswuy]

Gale Banks has an interesting video on youtube about their development of their diff covers. Testing showed that poor design of some aftermarket covers actually made the oil run hotter than stock covers. I am not saying your covers caused the problem, it is obvious that the drain passages were the culprit, but the video is very informative.

 

[stangmata]

The Jeep is doing well and there aren’t any leaks. Also, thanks for the video recommendation. I’ll take a look.

As for the Comanche.