Rusty - I think Lionel has 'fessed up about their truck problems on the cylindrical hoppers:
"Now back in the [AF] lineup, Lionel's first S Scale freight car returns with an improved truck design that reduces ride height and simplifies conversion to scale wheels and couplers!" (p. 216)
I also saw this on eBay (from Trainz): Lionel part number 6-49081 pair of hi-rail 70-ton, roller bearing, sprung trucks w/AF couplers:
https://www.ebay.com/itm/Ameri...8:g:7skAAOSwKSlcOHq9
Are these replacements for the 'too tall' trucks?
- Rich