Mustang V8 C4 Transmission Cooling Line (1966) Installation Instructions

Tools Required:
  • 1/2-inch Open End Wrench or Line Wrench
  • 9/16-inch Open End Wrench
  • Container to catch Transmission Fluid
Install Difficulty:
  • Easy
  • Easy Project
1. Start the installation of your new Mustang transmission cooling line with a cool engine. If you choose to use jack stands or ramps, consult the manufacturer’s instructions on their use. Put the car in park. Chock the wheels. Remove the keys to ensure that no one attempts to start the car while you are under it.
2. Locate the transmission coolant line connections at the bottom of the Mustang radiator. Place an oil catch pan under the radiator, just below where the coolant lines attach. Use 9/16-inch wrench to prevent the brass fitting in the radiator from turning while you loosen the fitting at the end of the transmission cooling lines with the 1/2-inch open end or line wrench. If the line fitting is stubborn and will not hold a wrench, you can cut the line with a tubing cutter and use a six point box end wrench to remove the fitting.
Mustang Transmission Cooling Line Install Image
3. Locate the coolant line fitting on the front of the transmission. On your C4 it will be located on the right side near the top just behind the Mustang bellhousing. Use the same procedure from step two to remove it.
Mustang Transmission Cooling Line Install Image
4. Now locate the rear transmission coolant line connection. It can be found on the right side near the back of the main body of the Mustang transmission. You will only need the 1/2-inch wrench to remove it since it is attached to an elbow. Now that the old lines are free, you can pull them completely out, making note of their path.
Mustang Transmission Cooling Line Install Image
5. Feed in the new lines from the front of the car towards the rear, one at a time, over the cross member and the steering linkage. Once the lines are in position, they pass alongside the Mustang oil pan and between the starter and the oil pan.
Mustang Transmission Cooling Line Install Image
6. Position the new Mustang transmission cooling line that attaches to the front of the transmission and thread the fitting in by hand and ensure that it is not cross threaded. The lines will likely need some slight bending at each connection to let the line seat squarely into the fittings. If the coolant line is not seated squarely, the fitting will not thread in properly. Now attach the line that attaches to the rear part of the transmission in the same manner.
7. Check that the new lines are in their proper locations and that they do not cross each other. Position the straight line into the left side of the radiator and the line that curves around the crank pulley to the right side. Align the fittings and hand tighten them. Once all the fittings are hand tight, you can use wrenches to tighten all four fittings. Remember to use the 9/16 to hold the 3 fittings stationary. Bend the lines (if necessary) to establish at least one inch of clearance around the crank pulley and to ensure that the lines do not rub anything along their entire length. Use the two provided Mustang transmission cooling line clips to fasten the lines together at the midpoint of the straight sections along the oil pan and near the starter.
Mustang Transmission Cooling Line Install Image
8. Replace any lost transmission fluid with new fluid. Start the car and check for leaks. If there are none, check the fluid again after the car is up to operating temperature. Add more fluid if required. The installation of your new Mustang transmission cooling line is now complete.