what is the tcc
Im going to assume the code you have given is PO740 on the obd2 scan tool? PO740 is a TCC circuit malfunction
it is in the transmission
Coolant Recovery Reservoir. There is no sensor in the coolant recovery tank on a 1998 Buick Regal.
take it to a transmission shop. The problem is in the tcc valve body.
Inside the transmission, on the valve body.
Trouble code P1860 means: TCC PWM Solenoid Circuit
yes
Is it located inside of the side transmission pan
Inside the transmission. It can be accessed with removal of the transmission pan.
Not sure what a TCC (Torque Converter Clutch) sensor is. There is however a TCC relay and a TCC solenoid. The TCC relay is found in the relay/fuse center and the TCC solenoid is located inside the transmission.
In the valve body, under the oil pan