Changing Diff fluid

Can I just use RTV sealant if I change the diff fluid, or is a gasket needed? And what type or weight of fluid is needed? I want to go synthetic.

Thanks!!

I replaced the gasket with a new one from NAPA and used Amsoil 75w-90 Severe gear lube with a bottle of diff lock additive. Check to see how much lube you need, mine needed just over two quarts. So I just bought 2 quarts and the bottle of diff lock additive and it was the perfect amount.

How do I know if I have limited slip? I have the tow package, and 3:73 gears I believe. 5.3v8

I do not see a tag on the diff.

chancers are you don't, There are two ways to tell. The fun way: mash on the throttle and see if you can spin the tire. or the boring way: look up your VIN#. Not sure which Letter or code will tell which you have, but I am sure someone on here has the answer

You dont need to remove the diff cover to change the fluid, there is a drain plug that can be opened with a 1/4" drive socket extention. So there is no need for a gasket.

I use the weight recommeded in the owners manual. Synthetic.

I like to remove the cover anyway, make sure there no debris in there. I just changed the wifes front and rear diff fluid on her jeep, and found some very fine metal in there.

Is there a place to lookup my vin and see what came with?
Thanks

On my truck there was no drain plug on my rear diff. So that doesn't apply to everyone. I also like taking the cover off just to get a look see at all the parts and make sure there are no surprises.