When should the timing belt be changed on a 97 T-100?

I've heard every 60,000 miles.

in 97 they decided to extend the change interval to 90,000 miles. the 3400 engine on this model has a very good record for not breaking. let it go til then and you should be fine. one note though, replace the water pump at the same time. if it isn't leaking yet, it will be soon and you'll save about 4.5 hours labor to remove the timing belt again and do the pump when it does finally go. the pump is about 100.00 and the extra labor is minimal compared to starting from scratch.

On my 1995 2wd T100 I waited until 100,000 miles and had both the timing belt and water pump replaced for around $400.00, in 2005 here in Salt Lake City, UT And yes I do have the 3.4 liter V6 engine.