Excessive gear / grinding noises while moving:
This can be a number of different things but is commonly the input carrier and sun gear which sits inside it. I have found this problem to be worse in the 1999-2001 models and can happen for no reason even on a low mileage transmission. It will start as a grinding noise that changes sound with speed and turns into crunching noises and finally loss of gears and all movement depending how far it goes. A lot of fine hard bits of metal will likely be in the pan or filter and a complete overhaul is the only remidy for this. Another cause of this noise can be a differential failing. The planet gears on the differential that sit inside the internal ring gear in the tail of the transmission can become very pitted and chip under high mileage and excessive stress and this can also happen if any debris is in the trans and travels through the cooler and back into the geartrain. Sometimes replacement of the differential can cure this, but normally the internal ring gear is damaged as well which requires complete overhaul.