Hello every one. I am planning to replace my rear and front differential fluids and also the transfer case fluid (Matic J). A few questions before I do this the first on my own.

1. I was advised by the dealer to use a little bit of RTV silicone gasket maker on the transfer case fill and drain plug to prevent any leaks. The dealer said there are no washers on the transfer case like that of oil drain. Is this true?

2. If RTV silicone is needed would a Permatex ultra Black Hi-Temp RTV silicon gasket maker work and do I need to wait for the silicone to set before adding fluid through the fill plug?

3. For the front and rear differential, does the copper gasket need to be replaced every time? I am under the impression that it does not have to be replaced every time unless it becomes damaged or deformed.

I have searched the forum in the DIY and youtube video. The general consensus is that differential gasket do not need to be replaced but I am not sure about the transfer case gasket.

Please advise and thank you.