'00 Venture Gear Shifting Clicking

Hi all,
Got a 2000 Chevy Venture and recently it started giving me those clicking sounds when the gear shifts to a higher one while I'm driving. Interestingly enough, the whole van "yokes" when the gear shifts up...
So, what I'm looking for is maybe for some reasons of why would it do that.
I know the engine very well, but this is new to me....
Could anyone please help?
Thank you very much,
Serge

sounds like torgue convertor or spline problem