Q: Replacing radiator having trouble connecting transmission coolant lines to new radiator.

Hello. You will leave the clips in and the lines will snap in place. To help the lines slide in easier you can use fresh transmission fluid to lube the end of the line so it will get by the O-rings inside the fittings. If you still cannot get them to snap in place then you can stick a piece of wood down next to the lines and use a pry bar to push the lines into place until they click in place. Make sure the line is going in straight so it does not break the seals in the fitting. If you need assistance, a certified technician from YourMechanic can come to your home or office to replace your coolant lines.