Delayed down shift could be dirty filter, valves or improper fluid level, the fluid level tolerance on those transmissions are very tight, it needs to be damn near exact. Slipping, varnished plates, needs rebuild. Or solenoid pack, easy swap. If shuddering, hopping when catching gears or leaking, tc. Fixing transmission problems can be pretty inexpensive if you know what to look for. Very expensive at the mercy of a mechanic.