Third Member Swap

No you dont need to replace but if you plan on keeping the car then have then checked out.
If you are doing it in your driveway or garage then, No it is not as easy as it sounds - it is a pain in the @SS.
Definitly use a gasket with permatex
the pumpkins are heavy
use Lucas oil stabilizer with your regular oil
try to keep your tranny from making a mess by keeping the driveshaft in the tail of the tranny
you may need to buy new crush washers for a leak free fit
you may want to purchase a siphon pump to easily fill the rear
keep your hands clean when removing/installing the rear brake backing plate otherwise you will have to change our back brakes - do not disco the brake lines
Clean the old gunk out and make sure you get any metal chunks out.

Go to Autozone or Advanced Auto and get an axle puller tool on their loaner program (no charge). Some have had luck reversing the brake drums and using as a slide hammer, but after a couple of hours getting nowhere with mine, I got one of these tools and made short work of it. My bearings were in good shape as well, so I did not replace them. I did use a scuff pad to clean up the surface of the races before putting them back in. Besides this, do as STSFCTN67 suggest and use crush washers, new gasket and permatex. I have had no leaks and the new 3.80 is awesome with the T5. Last thing, that chunk is heavy, make sure you use a jack to support the weight as you are removing it.

A simple way to determine if the axle bearing(s) are bad, once you have the axles removed from the housing, is to place your thumb against the outer edge of the bearing and give it a swift spinning motion.

If the bearing turns more than 1 full revolution, it's bad. The sealed axle bearings are lubricated at the time they are manufactured. The lube is thick and places a good deal of resistance on the bearing from freely spinning. If the bearing spins easily, the lubricant has been used up.

If you're spending money on a new 3rd member and going to have the rear end apart anyway, this is the time to replace axle bearings and seals.

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