tranny line leaking

the pipes running underneath the driver's side door is leaking near where you jack up the car how do i fix it and where can i get the part thanks

If it's under the Driver's door it's probably the radiator return tube. There's a drain plug in the tube, make sure it's not loose - if it's not the cause of the leak you'll need to replace the entire tube with a junkyard replacement or a brand new one (I'm fairly certain it's a Pontiac Dealer only item)

The lines under the left side are also Transmission cooling lines. The lines are covered with a spring like coil that has to be removed when you do a repair to the lines. I recently did this repair and used a Dremmel to cut the "coil" off th outside of the line. The line is a 5/16" "TRANSMISSION LINE" and can be replaced with a hose for transmission fluid. I used a double clamp method to be sure that the line stays secure. If you want to you can remove the rear water hose clamp(holds the 3 lines against the floor) to get better access to the tranny lines. Also check the lines at the transmission hsng for leakage too. Replace the clamps there too if needed. Then go to a car wash and high pressure the entire left side undercarriage and get all the fluid off. Pay attention to the rear brake area as the fluid most likely has gotten on the rotor and brake pads. Easy fix cheap money. But be sure and use 5/16" Tranny line hose.

OOPS! Forgot about tranny cooler lines, must be because I have a 5 speed. Those coil things are a pain, brake lines have em too. If you're having problems with rusty lines, make sure you catch any unibody rust before it gets out of hand and wrecks the frame. Sand blasting the underside of the car followed by a rubberized undercoat is a good idea on any car driven where roads are salted in the winter. You can also use flexible copper tubing for the tranny lines.