Timing chain failure

Ran accorss this sub over on reddit. Which brings to mind, how long should chains last ? Ive had other chain driven motors with proper maintenance, hit 200k with out a problem.

Obviously this is an isolated defect especially at such low miles.

https://www.reddit.com/r/Justrolledintotheshop/comments/uka1io/7_miles_on_the_engine_tacoma/


The main crank sprocket came off, when pulling the cover off, havent seen that before.

 

dealerships will tell you chains should last the life of the engine but i think the reality is they can stretch, fail, tensioners can also break down etc.

 

I'll still take a timing chain over a timing belt, though.

 

sounds like it wasn't torqued properly at the factory just like the u-bolts on the rear axle.

 

funny thing is they aren't lying - it does last the life of the engine. the engine's life ends when the chain ends haha

 

When has anyone or anyone you know have a timing chain fail? Me, never.

 

its usually the tensioners for the chain that fail and it skips a tooth.

 

are these interference engines (i forget the exact term) where the pistons and valves get real friendly when the chain breaks/slips?

 

good question - i'm not sure about the 3.5 or the 4.0. I know the 3.4 was.

 

Man these 3rd gen 3.5's are failing left and right.

 

The 3.4L in the 1st gen Tacomas is a non-interference engine. If the timing belt breaks you're stranded, but it won't harm the engine.

 

Tesioners? Yes. 2 older Toyo. trucks.

 

The move from chains to belts was to eliminate stretching, jumping, reduce rotating mass and increase valve precision.

Even in the 70s, 100k was a decent life for a chain.

Chains came back because quality/precision increased and complaints about required PM om belts

 

huh just did some digging and it looks like you are right. i had a 3.4 in my 4runner for years and always assumed it was interference

 

7 miles? Thats an assembly error for sure.

Also curious to know if the 3.5 is an interference engine?

 

I find sorta conflicting assumptions regarding the 4.0 but most seem to say it's interference. I know the 22re of old and 2.7 were chain driven interference engines

 

Out of the 1.25 million plus sold how many have you seen???

And thats just Tacoma 3.5's they're in several other models also.

 

A bunch.

 

I've seen way more 2nd gens with frame rot.....