Yes, 481 went into service in July or August, 1981. Until then there was usually a single 470 on train 461 and a doubleheader of 470's on train 463.
At this time the D&S only had the D&RGW's passenger car roster to work with, which was 22 coaches of various types and the 3 business cars. A single 470 had been cut back to 10 cars by the Grande rebuilding the San Juan cars with steel sides. The D&S may have cut them back even further to 9 cars. One of the business cars (usually B-2) was on every day, leaving a 14 car train to doublehead to Silverton. Back then, I think 15 is the absolute limit for the Silverton wye.
When the started running 481 they put her on the 14 car train. That's when they found that 480's don't like to pull maximum tonnage at 15 mph.
In addition, somewhere in there, box cars began to show up in the consists too, to haul LCL to Ah! Wilderness.