Our 2006 GX470 started making a slight knocking sound on cold starts in the morning around 22K miles. By 25K miles it was no longer in our imagination, this was a real sound, but the dealer could not repro. By 30K miles, it was very loud and easy to reproduce. Everyone in the car can hear it. Not only every morning when cold, but sometimes even when the engine is warm. Of course, the dealer could not reproduce. Finally, at 33K miles, I'm worried about the integrity of the engine and take it to a different dealer. Attending the cold-start test the next morning, I get them to confirm it's a real sound. Great, they hear this knocking noise that has gotten much louder and is causing our GX to sound like a Ford Station Wagon from 1970.

Please note, we only use premium fuel. The sound is loudest when cold and between 500 and 1000 rpm. But as the symptom progresses, it can be heard more readily when the vehicle is warm or even at higher rpms.

The findings from the second dealer (and third visit) came back today: Normal exhaust gas noise. They claim that this is a common issue with this model and it's nothing to worry about.

Keeping in mind that this donk-donk-donk-donk knocking is MUCH LOUDER than the drive-shaft clunk we experienced when the car was new, I cannot believe that people are ignoring this noise issue and accepting it when the clunk sent so many of us to the dealership. So I'm curious. How many of you have a GX with more than 30K miles that is making knocking sounds in drive or reverse, pulling out of your driveway when the engine is cold?

I am having the same problem with my 06'. Only when it is cold though. As soon as it warm up, it stops. I was thinking it was the type of oil or possible bad oil pump. Do you have any updates on your efforts?

Thanks

My 2007 does it too but to a lesser degree than yours. It started around 15,000 miles and it only does it for a few minutes when I first turn the car on in the morning and it is more noticeable when it's cold. What's odd though is it always happens when the car is in reverse but not always in drive. When I first start the car while in park it may not happen, but as soon as I put it in reverse it starts. By the time I buckle my seat belt, tune the radio, back down the driveway and into the street the knocking stops. I don't think it's ever returned during the day, even on really cold winter days.


The dealer couldn't replicate even when I dropped the car off the night before and told them that a technician needed to start the car first in the morning and not the lot jockey. The next time it needs servicing I will drop it off the day before and tell the service technician that I will return in the morning because I want to be in the car when the technician starts it so that I can replicate the problem. I'll leave a note on the steering wheel too as a reminder.

I am experiencing exactly what you have been, however I just was able to duplicate the knock when the engine is warm. Put your foot on the brake and give give it a little gas. You will hear the knock. I guess I have to get to the dealer as well but please keep me posted on your findings with service as well.

Thanks

The knock is due to the Knock Sensor. There are 2 Sensors which needs to be replaced and also the Exhaust Valve Clearance ( Cold Shims. The Engine is perfect. The sensors needs to be replaced and cannot be adjusted as the readings stored on the ECM has different values. Now coming to the Exhaust Valve the clearance on the shims that has been installed ask the dealer what exactly are the readings. There is a chart reference which the dealers have. I believe there was Bulletin issued for replacement on your model with a higher value mm shim. I exactly do not know the values .