How to Replace Transmission Lines on Vehicles

by Contributing Writer; Updated June 12, 2017

Vehicles equipped with an automatic transmission, utilize an automatic transmission fluid cooler integrated into the radiator, to maintain proper operating temperatures within the transmission. Automatic transmission fluid flows through a steel and rubber line to the cooler in the radiator, where air drawn in from outside the Vehicles by the engine fan draws heat off the fluid, which then returns to the transmission through another steel and rubber line. Over time, these lines may begin to leak causing low fluid levels in your transmission. Driving your Vehicles with a low transmission fluid level can cause serious damage to your transmission.

Under The Hood:

 How to Replace Transmission Lines on Ford Trucks

Removing the Transmission Lines on a Ford Truck

Raise the vehicle and support with jack stands underneath the frame or axles.

Drain the transmission fluid. Locate the transmission pan drain plug underneath the transmission. Place a waste oil collection pan underneath the plug, and remove it using an appropriate sized wrench. When all the transmission fluid has drained out, replace the drain plug.

Using a wrench, remove the transmission line fittings from the side of the transmission.

Using a wrench, remove the transmission line fittings from the radiator.

Using a socket, remove the brackets that secure the transmission lines to the vehicle's frame.

Remove the transmission lines from the vehicle.

Installing New Transmission Lines on a Ford Truck

Lift the new transmission lines into position along the vehicle's frame.

Reinstall the brackets that secure the transmission lines to the frame.

Using a wrench, thread the transmission line fittings into the radiator. Tighten the fittings.

Using a wrench, thread the transmission line fittings into the side of the transmission. Tighten the fittings.

Fill the transmission with the appropriate amount of fresh automatic transmission fluid. Consult the owners manual for your vehicle to find the appropriate amount.

Lower the vehicle.

Run the engine and visually inspect the transmission lines for leaks.

Items you will need

  • Automotive jack

  • Jack stands

  • Wrench

  • Waste oil collection pan

  • Socket set

  • Automatic transmission fluid

 How to Replace the Transmission Lines in a Chevrolet Cavalier

Raise the car using a jack and support it on jack stands. Chock the rear wheels and disconnect the negative battery terminal using a battery terminal wrench.

Disconnect both transmission lines from the radiator using a flare-nut wrench. Place a bucket underneath the radiator to catch any dripping transmission fluid.

Crawl underneath the car and locate the transmission line fittings on the transmission. Disconnect both of the lines from the transmission using the flare-nut wrench.

Compare the old transmission lines to the new lines to ensure that they are the correct size. Crawl underneath the car and connect the new lines to the transmission with the flare-nut wrench.

Connect the new lines to the radiator using the flare-nut wrench. Lower the car, reconnect the negative battery terminal using the battery terminal wrench and start the engine.

Examine the hoses and connections for leaks. Check the transmission fluid level and add fluid if necessary.

Items you will need

  • Automotive jack

  • Jack stands

  • Wheel chocks

  • Battery terminal wrench

  • Bucket

  • Flare-nut wrench set

 How to Replace the Transmission Lines in a Chevy Cavalier

Raise the front of your Cavalier off the ground, using a jack, and place a pair of jack stands under the frame to support the Cavalier. Position an oil drain pan under the radiator where the transmission lines meet the radiator.

Loosen the fitting on the end of one transmission line at the radiator with a wrench, then pull the line down and let any transmission fluid drip into the drain pan. Move to the other end of the line, where it meets the transmission, and place a second drain pan under the lines.

Loosen the fitting on the transmission end of the line you're working on, using a wrench, then pull the line out from under the car. Slide a new line in place, attaching it to the transmission first. Tighten the fitting with a wrench.

Raise the line to the hole on the radiator and thread the fitting in place. Tighten the fitting with a wrench until it is tight. Repeat the process for the second line. Remove the drain pans from under the car.

Raise the car off the jack stands with your jack, remove the jack stands and lower the car to the ground. Remove the jack from under the car.

Items you will need

  • Jack

  • Jack stands

  • Oil drain pans

  • Wrench set