i dont see the need to replace them if they are not worn out. there are a bunch of zurt fittings on your drive(prop) shaft both the main and the front(for the 4wd). i would give them each about 5-6 pumps each then drive it for a few days and repeat untill the noise goes away. make sure you drive it in 4wd too(4hi is fine) so the front shaft gets greased