Finally found something.

It's an arcticle comparing the GWB (Gravitational Wave Background) to the CMB (Cosmic Microwave Background) and is pretty cool in it's own right... and it says:

"...the GWB would be redshifted, like the CMB. But because of the GWB's earlier provenance, the reshifting would be even more dramatic: the energy (and frequency) of the waves would be downshifted by 24 orders of magnitude."

http://www.aip.org/pnu/2007/split/809-1.html

It's a pretty obscure reference, but for my money gravity is redshifted by expansion.

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If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it... of the manifestations of the profoundest reason and the most radiant beauty, which are only accessible to our reason in their most elementary forms...
Albert Einstein