Change timing chain?

[RIP]

I've seen a few threads about timing chains lately. The time change interval for timing belts is well established. The interval for chains isn't so clear. I just wander if anyone has an idea or has a difinitive word on when you should consider changing a timing chain? My 96 GC with the 3.8 ltr is hitting 180K miles. I'm thinking 200K is reasonable. What say you?

Has anybody changed one. I'm thinking the engine has to come out correct?

[MT-2500]

They usuall outlast the engine.
Drive it untill it drops or blows.
MY

[KManiac]

First of all, I would like to point out the differences between a timing chain and a timing belt.

The timing belt is a continuous, fabric reinforced, rubber belt with rubber teeth. The installed belt is kept taught with the help of a tensioner. The advantages of a timing belt is that they don't stretch with age and, being lightweight, take less power off the engine to operate. They are also very quiet. The disadvantage is that it is prone to sudden and catastrophic failure and there is no way to accurately predict when they will fail. Timing belts can fail in two ways, either by breaking or by stripping out the rubber teeth. Either way, the car must be towed.

Timing chains are assemblies that are similar to a chain on a bicycle. As a timing chain ages, the wear in the link joints causes the chain to elongate over time, causing a slow retardation of the cam timing over time. This is a disadvantage of the chain over a belt. However, the amount of "slop" in a timing chain can be measured. This can be done by rotating the crank in the opposite direction of normal rotation until you line up the timing mark on TDC. Next, reverse the rotation of the crank until the cam starts to move. The difference in the position of the timing mark will tell you how many degress of slop you have in your chain. This is an advantage of a chain over a belt. I would replace any chain with 9 or more degrees of slop. The first failure mode of a worn out timing chain is skipping a tooth. Very rarely do they ever break. When a timing chain skips a tooth, the vehicle in most cases can still be driven, although they are sluggish and difficult to keep running.

If you are concerned about your timing chain, then I would attempt to measure the slop to verify how worn you chain really is. Good luck and let us know what you find.

[KManiac]

By the way, I have changed the timing chain sets in four of my 1964 Chryslers. However, I have never attempted this in a modern mini-van. My 1998 Town&Country LX has only 87,000 miles, so I don't expect to try this for some time. You don't have to remove the engine to do this. Just remove everything from the front (drive-belt side) of the engine to access.

[HeadlessHorseman]

226,000 miles on my '96 GC LE with a 3.8L and NO problems whatsoever.

[RIP]

Thanks for all the info. The engine is running just fine. My only concern is if there is a recommended change interval for a timing chain I'd hate to find out about it after it goes. The only catastrophic 3.8 ltr failure i've read about on this forum was at 220K+ miles and the crank snapped. Looks like MT-2500 has it right. Cheers!