The 4.7L V8's have a Timing Belt. It is recommended to be changed every 60,000 miles, or at least checked at that point. I always recommend changing it at that time, because if you don't you'll screw up the engine pretty bad if it breaks. It is an interference engine, so if the belt breaks the pistons will hit and either bend or break the valves and lifters.

 

Wow 60K that sucks
The 3.4 V6 is every 90K

 

Great, thanks. I just did a timing belt on my toy 300ZX and don't really want to do that again........

 

Belts being replaced keeps the engine running smoothly. I remember a lot of the old v-8's having belts so loose, you could practically remove the chain and leave the gears on. The belts are smoother and quieter. Problem is they made the engine interference at the same time. My Lexus v6 ran a couple thousand short of 180k when the water pump went and the belt still looked pretty good. I had a dodge that went a couple of hundred before it was due, luckily it was not an interference motor.

 

My Jeep has a timing chain, and I don't get anymore noise from it than I did with the Nissan pickup I had which had a timing belt. I just think its a way to get a customer to spend more money by having to replace the timing belt which the shop always rapes the customer for, not just on parts but on labor too. They also throw in the extra cost of replacing the water pump which unless its not working is just another raping of the customer.

 

Interval for changeout is 90k on the Tundra 4.7L.

 

Less rotating mass. Easier maintenance.

 

Easier maintenance would be timing gears or timing chain. I've never had to replace a timing chain in any vehicle. I've had to replace timing belts and its a PIA.

 

<- not a pro

I've been told that timing chains will stretch but last longer. A stretched chain leads to bad timing resulting in slow damage and worse gas mileage. A timing belt does not stretch but does not last as long as a chain. A belt is however much cheaper and easier to change than a chain.

New belt technology is available using highly-saturated nitrile (HSN), a high temp neoprene, rather than fiberglass reinforced belts. HSN is supposed to last a lot longer and they say they could eliminate periodic belt changes. Unfortunately, HSN belts are only being made for vehicles that came with it from the factory and they cost more than regular belts.

I wonder if the computer controlled VVTi would adjust for a broken timing belt or chain to reduce engine damage.