Bathurst winner Jason Bright has replaced Matthew Brabham in Preston Hire Racing's PIRTEK Enduro Cup line-up.
Bright, who retired from full-time Supercars competition at the end of 2017 after 19 seasons, will partner Lee Holdsworth in the team's #18 ZB Commodore.
Brabham was signed by Charlie Schwerkolt at the start of the year for a maiden enduro campaign.
Having spent the bulk of his career in single-seaters, though, the 24-year-old has found the transition difficult with limited running.
"Our team has made a really tough call and has asked Matt Brabham to step aside for our 2018 Enduro campaign," Schwerkolt said.
"Our category is so competitive and with limited test days it makes it incredibly difficult to get up to speed.
"Matty's an amazing guy with incredible potential. The team and I are really thankful for his time and we look forward to seeing him again soon with Preston Hire Racing.
"I'd really like to welcome Jason Bright in joining the team and filling in at such short notice.
"He has a wealth of experience and look forward to seeing what he can bring to the team."
Bright made his final full-time start in Newcastle last November
Bright missed out on a 2018 co-driver role after bowing out with Tickford Racing, but will make his 22nd Great Race start after all.
He finished eighth at Bathurst with Garry Jacobson last October, having made the ARMOR ALL Top 10 Shootout.
The 45-year-old conquered Mount Panorama in 1998 with Stone Brothers Racing, and has two more podiums to his name.
Bright visited the team's Melbourne workshop on Thursday but the outfit has exhausted its testing 2018 allocation.
That means ride days will be the extent of his time in the Preston Hire Commodore before September's RABBLE.club Sandown 500.
Brabham made a one-off Supercars start with Lucas Dumbrell Motorsport at Barbagallo Raceway in 2017, and his primary '18 campaign is in Stadium Super Trucks.
He drove Holdsworth's Commodore at Sydney Motorsport Park's pre-season test day, then in practice sessions at Barbagallo, Winton and Queensland Raceway.
Last Friday at the Coates Hire Ipswich SuperSprint, Brabham finished at the foot of the times in the dedicated co-driver session.
A late-May Winton test day was curtailed by a crash with Brabham behind the wheel, further limiting his mileage.
The 2018 PIRTEK Enduro Cup starts at Sandown on September 14-16.