The sealed ball bearings used on all modern cars are not single row ball bearings. They are double row ball bearings (angular contact) with deep groove races and designed to take side loads. One row of balls takes a thrust load in one direction, and the other in the other, so when you are placing a side load on the bearing in either direction there is a thrust bearing taking the load.
The commonly used ball bearings used to replace tapered roller (thrust) bearings in mopar 8 3/4's are NOT thrust bearings. They are single row shallow race radial contact bearings, and with extended side loads will fail.
See this link for schematics
http://www.engineersedge.com/bearing_types_pic.htm
Although "green" bearings resemble other sealed wheel bearings, they are internally a very different animal.
