Hey you G56 experts, I went with AMZ/OIL's 9.9 pint fluid refill and ordered 5 quarts of the Manual Transmission & Transaxle Gear Lube 75W-90 for a friends 13 DRW. Not even close to the fill hole! Really sucks because we had to go to NAPA and pay $4 per quart more than my cost. So it took 6.5 quarts to fill to where it was running out the fill hole. Truck was setting on my level shop floor.
I did a search online and came up with the same 9.9 pints. Seems way off to me!
I assume this should be ok as he does not tow heavy.
At photowrite's suggestion, I am running redline MT 90 which my transmission shifts better than the amsoil Torqueshift I had in it for 1 year. I haven't driven it with the MT 90 in freezing weather though, so I don't know if it acts different in the cold. I have the fast coolers, so mine takes more than 6.5 quarts. I overfill slightly through the shift boot to make sure the front bearings are lubed going up hill. IIRC, I've got 9 quarts. The fast coolers take an quart each, but they also allow a 1.5 quart overfill because they reach way above the fill hole.