Jim, Timing chains on those engines don't just break. I'd bet 10 to 1 that it was mechanic error. Most likely the timing chain tensioner was not properly installed. It is a ratcheting device. The inner plunger that pushes tension on the chain can not go backwards (to provide slack on the chain). To make matters worse there is a spring inside pushing the plunger out (tight on the chain) If during disassembly the chain was allowed to go slack before the spring was removed it will push the tensioner plunger out on it's own accord. Problem is, when reinstalled like this there is too much tension on the chain and the ratchet mechanism will not allow it to release. You actually have to push the plunger all the way out and put it back in the other side to re-set it. Most likely cause of failure is excessive tension caused as described. Given the relatively short distance it lived this scenario is only more likely, as they will not live long assembled like that. I'm having a hard time from the description you gave to detrmine the extent of damage. Sounds like you're screwed, and it's their fault. If you need more help on this one feel free to PM me. I'm a 10yr indie tech who happens to own a 4-matic myself. Not to mention I'm was a Saab guy until my 97 900SE coupe (22psi ) was totaled earlier this year.