Well I took my MDX to a local Honda dealership (Acura dealership is 1 hour away) for the transmission and transfer assembly fluid change. The techs there did not have a clue about it. (If your not trained in it then you can't falt them for not knowing) Then an older tech came back from lunch and new what I was talking about. He told me that the Pilot's transfer assembly uses the tranny fluid for lubrication but the Ridgeline uses the hypoid fluid like my MDX. He figures the other techs will be getting in services soon. But since they were not official trained to do it, he was not going to try on changing it on my MDX but did insist this is something I could do my self. So I set out to do just that.
Both washers are the same size as that of the fill crush washer for the rear diff. The honda dealership part number (as it reads on my invoice) is: 94109-20000 Washer, D 90400 Both bolts (drain and fill) are torqued at 33 ft/lbs per service manual. A SAE 90 or SAE 80W-90 hypoid gear oil, API classified GL4 or GL5 is recommended per service manual. I am using a synthetic Mobil 1 75W-90 hypoid gear oil. I don't know if this will damage the transfer assembly or not but I will post if there are any changes.
Here is a little info I found on the net that talks about the difference of gear oil and hypoid gear oil:
"Hypoid" is not really a question of oil, so much as a question of gearcutting. Old (1920's) rear axles used straight bevel gears to form the crownwheel and pinion. These had two disadvantage, the pinion shaft meets the crownwheel on its central axis, and the straight cut gears are noisy. By using a more complex "hypoid" gear tooth shape (if you look at a pinion, the teeth appear twisted) these problems can be addressed. The more gradual engagement of the teeth along their length reduces noise. By careful design of the geometry the pinion can be made to mesh _below_ the axis of the crownwheel. As the centre height of the crownwheel is fixed by the wheel height, this allows the propshaft to be lowered relative to the car body, giving a clearer floorpan and lower centre of gravity for better cornering. Hypoid bevels are now universal in this application. Because of the sliding contact that hypoid gears make, their hydrodynamic contact pressure is higher. To be suitable for use with hypoid gears, a lubricant must be capable of resisting high pressures. Oils with "EP" ratings (Extreme Pressure) such as EP90 are required. Some brands describe themselves as "hypoid" instead, a term which is synonymous with EP. GL-5 is a formal API standard for this type of oil (comparable to MIL-L-2105B/C/D)
Any way here is a pic of where the transfer assembly is located
And a closer pic to see the fill and drain bolts
And the tool I use for the VTM fluid change and the transfer assembly fluid change
Hope this info helps.