By Akash Sriram

(Reuters) -Tesla finance chief Zachary Kirkhorn has stepped down, surprising analysts who considered the 13-year veteran as a possible successor to CEO Elon Musk.

Shares of the world's most valuable car company were down 1% in trading after the bell.

The company did not give a reason for his exit. Accounting head Vaibhav Taneja, who joined Tesla through the $2.6 billion deal for Solarcity in 2016, will replace Kirkhorn.

His departure has raised concerns about a succession plan at the world's most valuable automaker led by Musk, who also holds key roles at SpaceX and X social media, formerly known as Twitter.

Soft-spoken Kirkhorn was seen as an effective balance to the more volatile Musk and was one of the most visible executives who often spoke on calls with analysts and made presentations on strategy and products.

"He was able to be an effective liaison communicator between Elon and other executives ...that would be a skillset that is hard to come by and very valuable but hard to quantify," said Thomas Martin, senior portfolio manager at Globalt Investments, a Tesla investor.

During Kirkhorn's tenure, Tesla posted its first quarterly profit after it launched the mass-market Model 3 compact sedan and hit a market valuation of more than $1 trillion.

"Being a part of this company is a special experience and I'm extremely proud of the work we've done together since I joined over 13 years ago," Kirkhorn said in a LinkedIn post.

Kirkhorn did not respond to queries when contacted on LinkedIn.

"That he's going to be around until the end of the year is evidence that this is just for personal reasons and the personal reason is likely that working with Elon Musk is really hard and he's done it for 13 years," said Gene Munster, managing partner at Deepwater Asset Management.

Kirkhorn's departure marks the biggest shake-up at the company since long-time executive Jerome Guillen, who oversaw its semi electric trucks, left in 2021.

"I would like to thank Zach Kirkhorn for his many contributions to Tesla over the course of 13 often difficult years. Much appreciated and best wishes for the next stage of his career," Musk said in a post on X.

Taneja, 45, takes on the role, or the so-called "Master of Coin" position, in addition to his job as chief accounting officer.

He spent nearly 17 years at PricewaterhouseCoopers, one of the big four accounting firms, before joining SolarCity in 2016, when Tesla bought the solar panels maker for $2.6 billion.

The Austin, Texas-based automaker this year cut the prices of its cars in a move that prioritized sales growth and market share and squeezed its industry-leading margins.

Tesla has also hinted at more price cuts in what Musk called "turbulent times" as rising borrowing costs take a toll on the sales of electric-vehicle makers.

(Reporting by Akash Sriram in Bengaluru; Editing by Savio D'Souza and Arun Koyyur)