I tend to count on my male folks to let me know when to stress about my car or not. Left to my own devices every little noise would get my heart rate up. Well, now my rear differential tried to explode on me. Can't even drive the Baja up the driveway to get it into the garage. Something about the clutch not having enough friction. The boys are coming round for beers and car work later so it is about to get pulled all apart. For now I have one picture of the crack in the rear differential. You'll note that there is oil actively leaking out of the rear differential so it wasn't that I lost lubrication and then it broke. 

 

 

Seems to me like one of those things that doesn't ever really happen. Anyone got any pointers or potential causes of the failure?

woah, nice!   thanks for the picture.

 

how many miles on the vehicle and was the rear diff fluid ever changed?

 

so rare it's hard to say.  an improper tow or mis-sized tire by a previous owner or infrequent oil changes would be just as likely as a random mechanical failure which is probably the case if you've owned it since new with none of those possibilities. 

 

by "infrequent" oil changes - these are robust and hardly require much maintenance, to cause damage it would likely have never been changed and has 10 year old fluid in it.

The rear diffs on these are under so little stress normally that the original gear oil will pretty much last the life of the car.

 

In the picture that gear oil looks pretty clean, so either

A: it's old and its clean because the rear diffs don't stress oil that much, or

B: someone recently changed it to cover up a condition of abuse, such as water contamination.

 

How many miles on the car? How long have you owned it? Has the rear diff fluid ever been changed during your ownership?

The diff could have been very low on oil. Low enough, that the remaining oil was not wetting the rotating parts. And that would have caused the diff to seize-up and 'explode'.

And I can't see on the photo where the oil is actually leaking out; does the crack extend down near to the bottom of the case? And is that where the remaining oil is leaking out?

As others have said, these diffs don't usually leak much oil, and can go for years without attention. But yours may be 'the exception that proves the rule'.

Hey Posters,

 

Thank you so much for replying. I purchased the Baja new. Every now and again we would check the rear differential oil to make sure the level is good and the oil was clean. I really haven't abused my poor Baja. At the time the car had about 115,000 miles on it. The oil was leaking out of the cracks in the casing. There were no leaks prior to the explosion event to give the broken bit away. It has been one of the vehicles of choice used in moving from apartment to apartment. But you really can't fit enough stuff in the back to be "too heavy". The worst load was when we hauled some carpet to the landfill. That was the first hint that anything could be wrong because there were some grindy type noises then that we were "going to look at later". The carpet wasn't very heavy based on the receipt from the landfill. Did put an OEM trailer hitch on it but only ever hauled a sport trailer from uhaul once that was less than half full of stuff. Does seem like the car suffered from a random mechanical failure based on everything you guys said. 

 

The boys tried to drive the car up the driveway so that we could get it in the garage. That's when the whole back of the casing fell off and the gears tumbled out. Coming up on the car you would have thought someone had already started taking things apart.  

 

 

Based on the amount of oil leaked out on the street and the mess on the driveway when it all fell apart, the boys think that it had plenty of oil in it when it failed. Also the oil really was a clean as it looked. Ultimately, I got a used rear differential with 45,000 miles on it and the boys installed it in the car. Gotta say though, all those little creaky sounds make me even more nervous though. My poor boys... Thanks again for all your info!

Your original post was 2/15, and follow up today. Guess all is well with the replacement diff. Installing a used diff was a smart move. That is what I would have done under the circumstances.