I have it too and no it is NOT normal and is a defect and don't let anyone tell you otherwise. I have had mine worked on twice now and it was fine for about 2 days then came back. Dealer is in the process of replacing both drive shafts as a third attempt to fix this issue.
If not fixed by 4th time, then lemon law time.
NOT acceptable on a $53K Luxury vehicle. Normally Lexus is great but the GX has been a cluster f*ck since it came out. 3 recalls, outside temp. gauge issues, vibration issues, driveline thumping issues, A/C issues, etc
The simple fact is that the GX was released at least a year too early. Lexus did not do the proper R&D before releasing to the public, now we are the ginny pigs.
Then to make matters worse, they release the 04' without fixing the issues.
The GX is the first unrealiable Lexus and it really sucks for us first time Lexus owners who have heard nothing but praise about the quality of Lexus.
I think if I do lemon law this thing, I will look at the VW Touareg