I am kind of curious as to the same thing. What areas should I grease and where? My truck has 77K and up to 36K the dealer was doing any and all maintenance however since then we have been doing the maintenance. As I was reading through the maintenance log I realized that it said lube the chasis and I was kind of wondering where?

 

If you break the seal and force the old grease out wouldn't the layer of grease that is being exposed to the elements protect the grease actually being used to lubricate

 

If the boot is sealed then there is no way to purge the old grease out. I work on gearboxes for a living and you can set seals to purge for grease or to retain for oil its as simple as flipping it around and installing it the other way. When a seal is set to purge it is installed so that the old grease can be pushed out. With a sealed system in theory the old grease has nowhere to which means you're packing more and more grease in there which can make it difficult for parts to move. Everything in my field that gets greased can also purge grease so I'm assuming all serviceable parts on vehicles are made to purge grease. But I have a feeling that a rubber boot would not contain enough pressure to prevent parts from moving. That's what I'm thinking but someone please correct me if I'm wrong.