Board Thread:Naruto Discussions/@comment-26508646-20150704031517/@comment-6769189-20150711204945

He could speak to Son because of Kuramas innate ability as a Tailed Beast to do so. Not because Kurama had his Chakra.

We don't have evidence that Naruto used anymore chakra than was needed to undo IT. He only used Kurama against Toneri.