One of the things we do a lot of today is not spending money on cars. We push oil changes too far beyond their due date, and we really don’t want to spend money repairing cars if there is any way of getting out of it. In this case a Saab owner’s front differential exploded, and the cost of repairs did outdo the vehicle’s value.
What caused the diff to explode? Hard to say, but I suspect the front universal joint failed, and the driver just drove on, ignoring the vibration until the top half of the diff came apart. I don’t really know that for sure, as the driveshaft was missing when we got the car, but some violent act blew the top of the diff off, plus the fact that there was a big hole in the steering rack right below the the universal joint.
In the end, we left the diff in place, but took out the axles to keep it from flopping out of the car. Getting the failed diff out would have required a lot of labor and it seems that if he kept all four wheels on the pavement, it shouldn’t go anywhere. To hold the front wheel bearings in we needed to disassemble the axles and bolt the front constant velocity joint stub axles back in. Having the front driveshaft out didn’t compromise the transfer case, there were no fluid leaks. Then topped the whole thing off with a new steering rack.
The Saab 9-7X is just a Chevrolet Trailblazer with it’s own bumper skin. It is full time awd, and it was unknown if the front driveshaft missing would be a problem for the awd electronics, and in the end there was no downside. As long as you weren’t in the slippery stuff, you would never notice how the truck drove. The repair was still expensive, but at least the guy can still drive his truck. As for the next owner…. it’s never a bad idea to have a mechanic look over a prospective purchase.