I have been getting noise for serveral months from my 06 GX 470 on cold starts in the morning, it sounds like a tapping sound coming from the back on the engine. The problem last for about 2-3 minutes every morning and sometime during the day, it occurs when I put the truck in reverse, or drive. I had the truck serviced in early May, the tech said my timing belt was going to break at anytime he replaced it but, that didn't solve the problem. On June 2 I took the truck back in to service only for the tech to tell me because it only last for about 3 minutes he can't really detect where it's coming from. Has anyone experienced this problem, is it normal for the timing belt to go out at 40,000 miles?. I am really considering trading this truck in?

I've been experiencing the same thing on my 2006 GX since 25K miles. See post:

http://us.lexusownersclub.com/forums/index...showtopic=47402

The techs so far have claimed it's normal exhaust pinging off the converter, but the noise keeps getting louder and louder. I can now hear it all the time. I cannot believe this is a "normal" noise.

I'm going in next week for major service and another round of complaining. This will be my fifth time at three different dealers trying to get this fixed. I hope they didn't make you pay for the timing belt replacement. Let me know if you learn anything else.