most likely this won't help one bit, but there was the exact same (and well known) issue on some earlier model years of the GX. i had a 2004 and it happened all the time. i'm not a DIY guy nor mechanically inclined so i don't remember what it was called. but at times it felt like someone was gently tapping the truck from behind when i would stop (and it made the same sound you're describing). again, probably not related or helpful but any lexus mechanic will remember that from the GX days and can tell you if it could possibly be the same thing.

 

That is exactly what it sounds. ALmost like something rolling around in the trunk. I just posed a thread " what would you do in this situation (dealer question)" asking for opinions they say its the rotors but they have resurfaced them twice and I think i should be asking for replacement.

 

I have been talking about this in my other thread and I realized I didn't update on the suggestion of putting the car in neutral while its still rolling and seeing if the noise didn't occur to rule out drive line issue. Even when in neutral and I come to a stop I still get the noise so I guess that rules out drive line issues...

 

installed new poly

 

Sorry, I updated the second thread I started on this but forgot to update this one. After the third time in the shop I insisted on a new master mechanic at lexus. Guy found air in the brake line. Lines were bled and now the car is perfect again. Nice work on the new poly. So satisfying to do your own work!