Sorry, overlooked you showed it as a 3.2% grade in your first post.

Video is interesting because something is really wrong here.

EMD doesn't show specs for a P4 on their website, but show a standard SD70Ace is rated at 155,000 pounds continuous tractive effort. Assuming a P4 would be 2/3 that, it should be about 103,350 cte at about 37% adhesion (assuming it is ballasted heavy) which should be within its capability at 10 mph. A 3GS21B at 1950 hp should be generating about 58,500 pounds TE at 10 mph and need about 23% adhesion.

With both P4s and the genset the tractive effort at 10 mph should be about 265,200 pounds. 3.2% is 64 pounds/ton resistance plus add some for normal rolling resistance and a little curvature say 70 pounds/ton resistance. 265,200/70 = 3,790 tons less the engines at 560 tons (ballasted heavy) leaves about 3,200 tons theoretical tonnage rating (22 loads at 143 tons).

From the video of the train you can see the second cut has several (6?) empty flats being used as spacers for overhanging loads. Assuming all loads are at 143 tons and the empties at 30 tons, the train should have only been about 3,600 tons - a little more than what the guesstimated tonnage rating should be. I estimate the trailing tonnage on the first cut of 10 loads to not exceed 1,430 tons and the second cut at 2,200 tons which assumes there aren't any 263k cars.

Note that on both cuts, the #2100 has all three engines running. (Is it my imagination or is the NRE unit with green and clean engines generating more visible exhaust aka particulates than the dirty ole EMDs?) On a 3GS this typically indicates that the throttle is in Run 6 or better. In Run 6 (75%) the consist still should have been capable of pulling about 2,280 trailing tons up the hill at 10 mph.

Looking at it another way the 10 loads of the first cut should be no more than 1,430 trailing tons plus 560 tons for the power is no more than 2,000 tons total @ 70 pounds/ton resistance requires 140,000 pounds tractive effort. At 10 mph you would need about 4,700 hp on a conventional DC consist. So why are three engines with 10,500+ potential struggling to move the first cut that a pair of GP39-2s could theoretically handle?

I'm impressed - by how poor the engines are pulling. The leaves and low joints are probably causing the P4's to derate to keep their feet. Even derating to 25% adhesion the P4s should be very capable of 67,000 pounds tractive effort which 67k+67k+58.5k = 192,500/70 = 2,750-560 = 2,190 trailing tons or 15 loads at 143 tons.

I don't see where the P4s are worth 2 cents in this application.