Uber's cofounder and former CEO Travis Kalanick is planning to sell $1.4 billion of stock in the company, or 29 percent of his stake, a source familiar with the arrangement told CNBC.

Kalanick, who last summer following controversy, would sell his shares as part of that will value the company at $48 billion. As originally reported by Bloomberg and confirmed by CNBC's source, Kalanick had wanted to sell as much as half of his stake in the company, but had to limit that amount due to agreements between the company and its buyers.

CNBC's source said that the sale was oversubscribed, so each party was only allowed to sell 58 percent of what they'd wanted.

GV, the venture arm of Google parent company Alphabet, is selling "significantly less" than half its stake, according to Bloomberg's sources. Meanwhile, Uber and Waymo, Alphabet's self-driving car company, are locked in a messy legal battle and CapitalG, a separate Alphabet venture firm, is leading a new investment in Uber-rival Lyft.

Uber declined to comment on the report. GV also declined to comment.