We always examine a failed transmission to determine why it failed. Transmissions can fail for a number of reasons. When a transmission is replaced, the transmission cooler in the radiator must be flushed out to keep shrapnel from the failed transmission out of the new transmission. If the flush is not done and shrapnel gets in, the life of the new transmission will be drastically shortened. By the way, you should select a qualified transmission expert to work on the transmission in your car, as it is a highly technical one.