Hey Allan,
It sounds as if you’re trying to morph between two Element objects and E3D doesn’t really work that way w/o resorting to an obj sequence.
I’m only guessing that what you want is that the front face extrudes outward then the back face eventually catches up, shrinking the extrusion & going out of frame. You say “fade” though so I’m not sure. If that’s the case, you might be able to go a different route by duplicating your Element layer and then turn off the front face so the extrusion is now separate.
With just one group though, you might experiment animating the particles Z size. Minor problem with that though is that it scales in both the Z+ and Z- axis simultaneously, making it very tricking to make it look like the back face catches up with the front. You might then fiddle with Replicator Position Z (or create a group Null) though & hide that problem since you have you text leave frame.
Perhaps someone has a more elegant solution, but at least this is a starting point.