The incident at Archer Hill in Wyoming occurred on November 4, 1996. Train NPST had three diesel units (UP 9111, UP 9122 and UP 3222) pulling 136 cars at 11,620 tons. The rear unit, UP 3222, tripped a relay and could not recover its load and the train stalled at the base of Archer Hill.. UP 844 was returning from excursion trips in Missouri and Arkansas and was immediately behind the stalled train.
After checking their fuel and water, the UP 844 crew called the Omaha dispatcher and received permission to proceed past the red signal and to the rear of the freight. The EOT was removed from the freight, the steam locomotive coupled to the freight train and an air test was made. The code of UP 844's rear end device was given to the engineer of the freight so he would be able to monitor the rear end brake pressure and control the entire train's braking.
The UP 844 pushed on the rear and once the engineer in UP 9111 opened his throttle the train slowly began to move. The train gets up to about 20 mph and is moving well when it is discovered the crew of the freight is about to go dead and a dog catch crew is on the way. The train stopped on the Archer grade (.67% westbound), a new crew arrived and the process was repeated. Finally the crest of Archer Hill was reached, the UP 844 was cut off and the original EOT device replaced. The NPST proceeded downhill under its own power while the UP 844 and its train followed.
For a detailed narrative of the entire incident see:
"Distributed Power with a 1943 Alco"
by: Jack Wheelihan
Railfan & Railroad Magazine, March 1997, p. 50-53
A second incident is described in the October, 1998 and January, 1999 issues of TRAINS magazine.
UP 844 was on its annual shakedown run to LaSalle, CO on July 8, 1998, when an intermodal freight proceeding it with a single SD60M (UP 6155) died approaching Nunn, CO. The intermodal train was able to coast down grade into Nunn where the UP 844 could get around it and couple to the front of UP 6155 and pull the dead engine and train to LaSalle where replacement power was waiting.
"Steam Rescues Diesel"
TRAINS Magazine, October 1998, p.32-33
"When UP's 4-8-4 comes to the rescue"
TRAINS Magazine, January 1999, p.106-107