Rear Diff Vibrating when turning left?

So basically in December I had a vibrating problem and in order to diagnose it I decided to change the rear diff oil as it has never been changed before. So turns out it was actually my transmission fluid that needed to be changed which completely erased the vibrations. However, a new vibration arised. When I turn left like coming out of a parking spot, the truck vibrates and then the vibration stops. I often found this problem when it was cold. Not sure if that is a correlation. So basically I was reading around and found a forum that described the same thing and I was lead to use Posi-Trac to fix the problem. That fixed the problem right away and lasted about 6 months until last week where it began to have the same problem.

Should I add another 7oz of Posi-Trac or flush the whole thing again? I am completely lost on what I should do

It is an 07 TRD Sport.

 

Did you use synthetic fluid?

 

I used Valvoline High Perf

$29 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 Gear Oil

 

I had the same thing happen. Added another small bottle of additive and it fixed the issue. It took maybe 4 days of normal driving to completely go away, considering the additive had to mix completely and apply itself to the plates.

 

These trucks do better with standard gear oil.
There’s been more issues running synthetic in the LSD, than running standard oil.
I’d try Lucas 80w90 standard oil. You’ll still need to add the LSD additive.

 

Thank you! It's pretty inexpensive so I'm just glad it wasn't the Trans fluid. That was a pain. I'll probably do that. Thanks again.