2DO
2LO
2OD
2OF
2OR
2OU
2UR
3DOF
3DOL
3DOR
3DUO
3FLU
3FOR
3FOU
3FRO
3FUD
3FUR
3LOD
3LOR
3LOU
3LUD
3LUR
3OLD
3ORD
3ORF
3OUD
3OUR
3ROD
3RUD
3UDO
3UFO
3URD
4DOUR
4DURO
4FLOR
4FOLD
4FORD
4FOUD
4FOUL
4FOUR
4FURL
4LORD
4LOUD
4LOUR
4LUDO
4OULD
4ROLF
4ROUL
5FLOUR
5FLUOR
5FUROL

Data Gathered from http://www.scrabblist.com