The firm has previously downsized its chain of autocentres by selling off 45 sites, but eventually decided the brand could not offer enough scope for expansion to consider retaining the business.
Nationwide Autocentres, which bought those first 45 sites, has agreed to buy the remainder of the business that last year reported a loss of £2 million.
Lex, which began trialling a rebranding of the service centres as RAC autocentres, had invested heavily in service levels to meet tough new standards.
However, Andy Harrison, chief executive of Lex Service, itself renaming as RAC in September, said: 'We have been unable to find a business model which matches RAC brand values.
'Lex Autocentres is more likely to achieve its potential as part of Nationwide Autocentres, which is focused exclusively on vehicle servicing and repairs.'
He added that Lex Service was still focused on expanding the brand to new areas, such as its investment in BSM, RAC Auto Windscreens and its legal and financial services.
Nationwide Autocentres is now the largest independent service network in the UK, with 143 centres. The firm plans to rebrand the outlets over the next six months.