as part of scheduled maintenance when to replace timing belt
timing belt replacement on 2004 Lexus GX470
It is an interference fit engine serious damage occurs if the belt brakes. Change interval is every 90,000 Miles or 108 Months.
I had mine replaced at 90,000 miles... It was due at 100,000 but didn't to chance it and while they were doing that expensive 90,000 service, it paid to have it done then.