[brad_man_72]

Originally Posted by 71 super

Is the slip joint at the trans not for the movement and the carrier bearing is exactly that a carrier OR support bearing?

That's exactly how the stock carrier bearing works because the carrier bearing rubber is very soft.
With the billet/poly carrier bearing the driveshaft is mounted solid to the frame and the rear end. So the trans slip yoke only slides if the engine is moving fore and aft in the frame.

In theory the engine should be mounted pretty sturdy to the frame, and the rear end is mounted solid to the moving suspension. I prefer not to mount something solid to the frame and solid to the moving suspension.
99% of every other multiple piece driveline setup they use a carrier bearing more solid than this style, they also will always have a slip yoke in the rear shaft to account for rear end movement unless IRS. In every single RWD one piece driveline that isn't in a newish corvette the shaft has a slip joint.

Exactly zero automotive manufactures us a carrier bearing as solid as the billet/poly unit. Not even for semi trucks. Not even with a slip in the rear shaft.