Gear oil question

[NY87GN]

So this is the 2nd post I am writing about the same issue, I am getting a grind from the rear at a slow roll, backwards and forwards. I recently had a “reputable mechanic” replace my rear fluid. I mentioned to him to add the posi additive and he seemed to acknowledge, but one never knows.
Question is, can I just add the additive in? or do I start over?
What gear oil is recommended and weight?

 

[pacecarta]

backwards or forward in a straight line doesn't disengage the posi clutches so whether he added posi dif lube or not .. thats not the answer

the bearings and gears dont need the special posi lube additive
the posi lube additive is to allow the posi clutches to slip against each other smoothly when they disengage rather than chatter which they will do without lube,
if theres no additive the posi chatter will be most noticable on a slow sharp turn when outer wheel will need to spin faster than the inner wheel

 

[NY87GN]

Could it be my u joints? .Anyone have any other inputs.. would be very appreciated.

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[87_we4]

Dry u joints will make a noise like that.

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