They're the worst riding engine I've ever had the misfortune to run or ride in.
In my personal experiences, if the MP36 engines are not running at either full power or in heavy dynamic brake, they have terrible terrible lateral anywhere from 20-80mph. Not being the right kind of engineer to say for sure, I can only guess that it's because the engines are so long and heavy on top of 4 axles. At high speeds the vibration can be quite violent.
A couple of weeks ago some officials from Utah were out at Caltrain riding in the MP36 engines, since they have apparently purchased some. The engineer of one of the trains they rode on said the engine did the typical lateral/vibration business at high speed and the officials didn't seem to think it was anything to write home about. For me, holding on for dear life shouldn't be "all in a day's work" but then again... maybe there's just not enough excitement in my life otherwise.
That is a fun ride, RJ. Last year, our local RR Club in Prescott took Amtrak to ABQ to ride the Rail Runner. Took it from downtown ABQ to the north terminal then headed back south to Belen. Waited for a few hours, visiting the Belen railroad sights, jumped back on the Rail Runner to downtown ABQ again. Yup, it's a fun ride.
Hay Curmudgeon you may have been riding some of that poor track that gave bad ride quality.
Loco may have been rough but I'll bet the cars road good. One thing to remember your almost sitting on top op the truck and may have improper shock control also which causes rough riding. I have ridden many a loco and each one has different ride qualities. Later RJD
I can't speak to the ride quality, but I think they are a pretty cool looking loco. I have a copy of Railroad model craftsman with demensional drawings of the engine.. I may take a crack at scratchbuilding one in 1:29.......someday.