First off the only reason I have my t4r is because he bought me mine for a wedding gift. So I am eternally indebted to him for that as well as my countless late night calls to come pull me out of wherever I got had gotten stuck out on the trails when I was a kid. He had a high speed vibration and a squeak that was driving him crazy. I told him to check his drive shaft he drive a 2nd gen tacoma. he found out that his carrier bearing was bad, and it had been bad the last owner sprayed the crap out of it with what looks like silicone spray.
It had about 1in of play when you grabbed on the drive shaft, only 1/8 is allowed according to dealer. But this was not the worst part.
I got to thinking why did this happen? We removed the entire drive shaft to make things easier for installation of the new part and inspection of the rest. When we went to grease the U-joints the rear one wouldn't take any grease. like the fitting was clogged. Then upon a closer look
It was being lubricated with metal shavings and rust
I have never seen one so bad that did not sound way worse. Clearly this had been like this for some time. I am amazed it did not grenade on him. Anyway that is all now he can go back to wheeling.