Center differential vs Transfer case and which fluid to use

I called the dealer about the various fluids in my 2006 Ram 1500 ST manual V6 Regular Cab RWD and cross checked it with the Advance Auto fluid spec sheet and the only thing I'm not able to map is the center differential and transfer case fluid.

The dealer says there's a center differential that should use "246 ATF" fluid.
a) Advance Auto doesn't carry such fluid and
b) I read the 246 implies 4wd or AWD and mine is RWD

The Advance printout doesn't list a center differential for any 2006 RAM 1500 models regardless of engine, transmission, or drive but instead lists "Transfer case fluid" and the spec for the V6 is ATF+4.
In this instance I read that a transfer case implies 4wd or AWD and mine is RWD.

So at this point my questions are:
a) Is a center differential the same thing as a transfer case?
b) Which does my manual V6 RWD have?
c) Which fluid should I be using?

Both irst time dodge owner and first time truck owner so thanks

I'm pretty sure you have a Getrag 238 transmission, since you say you've a manual.

http://www.carquestprofessionals.com/catalogs/chemicals/V-8070 Manual Transmission Fluid Application Guide 6.6.13.pdf shows Valvoline products by year and transmission.

Long story short, if your truck is 2WD, there is no power divider in the driveline, as you don't have a front axle to power. A center diff varies a torque division based upon wheel speeds front and rear. A transfer case has a fixed division (ususally something like 40% front/60% rear) and additionally has ranges. LO ranges are underdriven for torque multiplication and HI is normal gearing. You could research them to see the particulars.

Looks like per the link above, you should use Syncromesh MTF regular fluid or ATF+4 synthetic fluid, as you like or per the manual.

EDIT: I wonder if what the Advance Auto clerk meant was the Getrag 238 uses the same transmission fluid as a NVG 246? Nonetheless, you can pick a brand of lubricant and almost certainly find application charts.