The brake lines on a 2003 Tahoe are made from steel and designed to resist corrosion. These lines run from the brake master cylinder to an ABS box just underneath the cab, then to each individual wheel in the front, with one line running to the back where it connects to the rear axle via a fitting.
Lift the Tahoe with the jack and put it on jack stands, with two stands underneath the axle and another two underneath the rear section of the frame. Crawl underneath the driver's side of the Tahoe and locate the ABS control box on the inside of the frame on the driver's side.2
Locate the steel brake line that runs from the ABS box at the front of the Tahoe to the T-fitting on the back of the Tahoe by the axle. Remove the fitting on the brake line at the ABS box and the axle fitting with a line wrench.3
Unbolt the clips holding the brake line in place with the 3/8-inch ratchet and socket. Pull the brake line off from the inside of the frame and away from the Tahoe. Lift the replacement brake line up into the frame and bolt it in place with the 3/8-inch ratchet and socket. Install the brake lines to the ABS box and the rear T-fitting with a line wrench.4
Take off the rear wheels on the axle with the tire iron. Locate the brake bleeder valve on the passenger side brake caliper. Slide the clear hose over the bleeder valve and slide the other end of the hose into the drain pan.5
Position the assistant in the driver's seat and have them start the Tahoe. Loosen the bleeder valve on the caliper with a line wrench, then have your assistant pump the brake pedal. Watch the brake fluid coming through the clear tubing, and when you don't see anymore air bubbles in the tubing, have the assistant hold down the brake pedal, then tighten the bleeder valve.6
Repeat steps 4 and 5 for the driver's side rear brake caliper. Reinstall the rear tires with the tire iron and lower the Tahoe off the jack stands with the jack.