Do your transmission lines trickle just a little ? Replace or repair leaking transmission cooling lines depends on the extent of the damage or condition of the lines. If the damage small such puncture or corrosion in a limited area, repairing the lines may be a cost-effective option. This typically involves patching or sealing the damaged section to stop the leak. Above all If the lines are severely corroded, have multiple leaks, replacement is often the safer and more reliable choice. New transmission cooler lines ensure proper functionality and reduce the risk of future leaks or failures. However replacing old lines with new ones can provide peace of mind and may be more time-efficient than repairing damaged lines. Ultimately, the decision should be based on the severity of the damage. The condition of the lines, and the long-term reliability of the repair.