3.8 timing chain rattle at low rpm

I have a '92 LaSabre with a 3.8. 115k miles. Took it in to replace the belt and water pump. When I got it back the timing chain makes a rattle at idle & low rpm. Goes away @ about 1300 rpm. It's very loud and embarrassing. My kids call it the "Uncle Buck" car. Please help me save my childrens childhood.

It sounds more like the harmonic balancer making noise by the way you described it. Take the belts off of the balancer pulley and put your hands on the pulley and try to turn it clockwise and counter-clockwise. If you detect any movement in the outer hub or pulley, it needs to be replaced.
By the way, welcome to AF!

Look for rubber seperation also.I did one one a Buick Riveria and the rubber part was seprerating.You need a special puller to remove the harmonic balancer for 1992 and up 3.8s and 3.3s.I know Carquest sells the puller Kent Moore does make the puller too for GM.

Could be timing chain too, though. At 115k miles it would be at the end of its life it has never been changed. Replacing the timing chain involves removing the front cover of the engine (which is a day-long job with hand tools, at least).

The rattling noise would be the damper having its plastic shield worn off and is now rubbing metal on metal. When/if you replace it, be sure to get a new damper with the chain/gear kit.