I'd love to hear the reason too.
Because Precision draws the line at one year. We can send it to them and have it rebuild for cost, that is what we offer anyone over the 1 year warranty.
The most likely cause is the thrust bearing is toast, which causes everything to move and leak oil out the back.
One thing to cover before someone else tears it down, pull the compressor cover and make sure the comp wheel has not contacted the compressor housing. If the wheel has hit, you cannot buy the wheel and it will have to be sent to Precision, so no sense paying two shops.
Also the $600 was a worst case high estimate, but its just a guess until the unit is looked over.
For anyone with a 71/72 the thrust bearing, even the new 360 thrust, is the weak link. If you let the charger bark alot, the thrust will fail faster. Teach yourself not to let the turbo bark and you will get a longer life.