Hi guys,

I recently had a new cover put on my rear diff. I'm not sure if the shop was smart enough to add the limited slip lube with the gear oil. Would it cause any problems if they didn't and if so, what kind of problems?
Since then (could be a coincidence) the rear end has been making a noise when I am driving very slow. I noticed it while creeping along at a Wendy's drive through. It's a tinging, grinding kind of noise (hard to explain), and it only seems to do it once I have driven for a while and the rear end is warmed up.
Is my diff screwed or do you think it just needs some lube??

 

Sounds kind of more like maybe it needs a U-joint.

If it's a posi and didn't get the friciton modifier additive, it might groan or chatter going around tight corners at low speeds.