Do you have to change the timing chain on a 1997 ford ranger 4.0 liter?

No, the 1997 Ford Ranger 4.0L engine uses a timing *belt*, not a timing chain. Timing belts are known to wear out and require replacement at recommended intervals (usually around 100,000 miles, but always check your owner's manual for the specific recommendation). Failure of a timing belt can cause catastrophic engine damage.