He didn't split from Hinduism. As Dave Rupa has said, Hinduism was not Hinduism back then either, but a loose collection of rituals and sacrafices made by Vedic Brahmins who had yet to assert authority as India's prime caste. In the Buddha's time, it was the Kshatriya that were the dominant caste and Kshatriya rulers gave patronage to all sorts of mendicants and brahmins, not solely to those following the Vedas.
The Blessed One was part of a society that had nothing to do with the Vedas, the Samanas or in SKT - Sramana. Wandering mendicant monks who espoused various doctrines and had followers of small or large amounts, Jainism also arises from this loose group of competing Samanas.
So contrary to the Hinducentric view that the Buddha was part of Hinduism and in fact an avatar of Vishnu, he categorically rejected the Vedas from the outset, refering to Vedic Priests as a "file of blind men" - http://www.accesstoinsight.org/tipitaka ... .than.html