question on hwy cruising

The weak part of the 7 1/4 is the spider gears, and to a lesser but related extent, the side gears. Pull your cover and check their condition. If there is any pitting on them or lots of backlash or play between the spiders and their shaft, replace them or the whole rear. If they look in good shape, button it back up, top it off with a good quality GL-5 gear oil and call it a day. Just drive it easy.....strain is what kills them. If I remember correctly, someone has high quality replacement spiders and side gears for these so you may want to upgrade if you choose to keep the 7 1/4.