Transfer case & Rear differential oil change.
 

NO! Hypoid gear oil is NOT the same as DPSF.

The front transfer case requires hypoid gear oil. It doesn't have to be Acura's. I usually use Mobil 1 75W-90. It helps to have a small fluid pump. The transfer case lube is typically replaced on the same schedule as the automatic transmission fluid, but they are completely separate. It doesn't need to get changed very often.

The rear differential requires Acura DPSF fluid. If you get confused, DPSF is embossed on the differential case right above the fill port. No joke. This is to remind people not to put VTM-4 fluid or anything else into the thing. ( VTM-4 fluid was used in 1st-gen MDXs ).

Always loosen the fill port first, then loosen the drain port. That way you know you can refill the thing after you drain it.

You need a small fluid pump, preferably not the same one you used for the hypoid gear oil or anything else. I keep my pumps in labelled ziplock bags to keep them clean. They don't need to be completely drained, just clean.

Service schedules aren't published for 2014 MDX, they go by the maintenance minder, but the "severe service" schedule is 1st change at 7500 miles, then every 15k miles thereafter. The severe service schedule is half the "normal service" schedule, so that works out to 1st change at about 15k miles then every 30k miles thereafter. The MM will shift the schedule to coincide with an oil change, as a matter of convenience to minimize service visits. The oil change interval is adjusted on the basis of driving conditions, but everything else is on a fixed schedule.

BTW, the Sport Hybrid rear differential is different from the mechanical SH-AWD rear differential. It does not use DPSF. I believe it uses hypoid gear oil, but I could be wrong.

Dunno. But rear diff service is code "6" on the MM ( maintenance minder ) display.

This is for SH-AWD, not FWD. It doesn't make much sense to replace rear differential fluid on a front wheel drive MDX, because there isn't a rear diff.

The Sport Hybrid has a very different mechanism. Per the Owner's Manual, Sport Hybrid requires "twin motor unit fluid", code 6 on the MM, and appears to have the same service schedule as SH-AWD, 15k miles then every 30k miles, or half those numbers for "severe service" in mountainous terrain.

If you are not completely comfortable doing the fluid change, I would ask to speak to a district Acura representative. I'm sure they will be very interested in this dealer's refusal to perform service that is required under the standard maintenance schedule. The SH-AWD rear differential is similar to a limited slip differential, and the fluid has friction modifiers that degrade over time. Failure to replenish these additives by changing the fluid will eventually cause the differential to shudder and may cause premature wear of the clutch plates in the differential.

The fluid change itself is trivial for any competent mechanic. But it does require the proper fluid.

This may just be a single incompetent service writer ( not exactly a novelty ). Are you located in the south, where AWD is less common?

An Acura dealer who's never done a rear diff change - and tells you to ignore the "6" minder code - is a dealer I'd avoid for most any work. IMHO.

Just a FYI, but the hybrids use ATF-DW1, 2.56 qts. Same for the DCT, but 3.7 qts, so it makes it somewhat easier to just get one fluid for all that drivetrain stuff.

As for Service Advisors, they are just sales people. Don't listen to them about anything technical, EVER. I'm sure all of you will agree that in your lifetime of driving and dealer services, you have probably only ever seen less than a handful competent SAs.