timing chain tensioner?

1997 328iC 115k Automatic

Whenever I start the car in the cool morning, it makes a rough start noise. But as soon as I put the car in drive, the noise goes away. It also makes the rough engine noise when the car is reversing.

When should the timing tensioner be replaces and how much would this job cost?

Thanks.

does the noise go away after the car warms up? the tensoner is hydrolic and should never need replacement. make sure your mechanical serp belt tensioners arnt the real problem.