I too have had a clunk noise in the rear end of my truck when slowing for a corner and then slightly speeding up. It’s done that since new. The dealer where I bought it also told me it was normal. I now have 100k miles on it and I hear a crunching sound from the rear going over a slight dip in the roadway. I’m going to check the springs and ubolts for torque or replacement.
Wow, you are tolerant to live with a noise for 11 years!
My 2005 does it too. The grease only works short term, in my experience. I didn’t use the “green grease”. Not sure if it would last longer. Some of the clunk, in my case, I think is just due to general drivetrain slack. Mine is older, with the 4 speed.
I think the above comments are likely correct, the source of the sound is the driveshaft slip joint. I wouldn’t expect there to be much of a problem with the rear leaf springs and u-bolts on a 2011. If lubing the driveshaft with a synthetic grease doesn’t do the trick, next in line
- driveshaft u-joints
- differential gear oil needs refreshing, esp if it is a limited slip , pos-itrak, etc design. These often require an slipperiness-modifier additive. Check the owner’s manual.