The dealer just did the 15K service. My thought was maybe they used the wrong weight.

 

If you will continue to service there, which I would seeing as how they fixed your car, I would check their work as far a which fluids go into your car, which filter they use for the oil, how much they charge.

Example:

I had a diff. and trans. fluid change. I was charged for 1 gallon of VTM-4 for the differential. It takes less than a quart, and VTM-4 is the reason I had a failure less than 48 hours later. They also put motor oil in the transmission. To me that's 3 strikes on the same pitch, so I just used another dealership to fix everything. I even had to fork over the money for another trans. service to get the correct fluid.

 

highly doubt that would cause the housing to crack..