Rear end grind sound

[NY87GN]

I'm a new owner of an 87 gn. I recently had my rear end fluid changed. I had mentioned to the mechanic who did the work to make sure that the fluid he uses is for posi. Not sure if I'm just being paranoid but, this morning took her out and as I am pulling in out backwards at a slow roll I noticed a grinding sound. As I pulled away.. nothing till I got to the traffic light and roll slow again.. it sounded like it came from the driver side.. any advice?
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[87_we4]

Check your brakes

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[NY87GN]

Many thanks!!

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[TurboBuRick]

Sounds like you need posi additive.

 

[Drewster]

X2 on the additive. GM brand works well


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