Any good FAQs online somewhere for Differential Fluid changes?

So far only

http://www.pavementsucks.com/tech/diff.php


And where is the "Once you think you have enough fluid" Line?

Also what weight gear oil should I use(no manual with truck) and is royal purple really worth it?

 

This one don't need a DIY. Pull the cover, let it drain out, clean out the inside with a rag, scrape off the old RTV sealant. Reapply new RTV, let sit a couple mins to "cure" then re-install.
Remove the fill hole and fill the diff thru the hole till fluid starts to come out. Plug the hole back up.

Only variable is if you have a LSD, then put a bottle of friction modifier in it when you have it about half full, then continue with the oil.

Oh, and if you do have the factory LSD, pray you don't find metal in the diff when you remove the cover.

 

What weight oil if I do very little towing?

 

75-140

 

You might also want to check my post at the following link.

https://dodgeforum.com/forum/3rd-gen...f-fluid-2.html