Ok to replace tensioners on a high mileage engine?

[cross6]

2004 4.0 Flex. 168,000 miles. No discernable chain rattle. (But I'm about to pull the valve covers for an inspection.)

I've seen several people (Al, etc) on here say the tensioners should be replaced every 100K or so.

My question is: If my cassettes are ok, is it safe to put new tensioners on such old guides? Will that break them when I torque them down?

I was hoping to make to reduce any slack with new tensioners and make it to 200K before pulling the engine and then just do a full rebuild.

thanks guys

 

[chopperb]

The tensioners are hydraulic on the 4.0. They do get weak over time. There is nothing wrong with replacing them at 168k. Kind of good insurance because a weak tensioner could cause the timing chain to jump at start up due to the tensioners bleeding down.