Unless I read the post wrong, the OP didn't say Chevy did a fluid analysis and saw the wrong fluid was in there...OP got his fluid changed at Grease Monkey, heard grinding, went back to Grease Monkey (sometime in about 1000 miles though he wasn't very clear on when he went back exactly), and it was Grease Monkey that confirmed the wrong fluid was used...at which point they changed the fluid to the correct fluid. The grinding didn't go away, and he then took the car to Chevy, who said the entire diff is blown. So Chevy never saw the car with the wrong fluid, they saw the car with a blown diff and concluded the reason was because of what the OP reported to them that the wrong viscosity was in there for about 1000 miles.

OP, isn't that the sequence of events?

If so, you have two fights on your hands, but this could help you. One, Chevy is denying warranty work for a part that is still under warranty because they say the wrong fluid grenaded the diff. Two, Grease Monkey will probably say no way the wrong fluid killed your diff in that short of a period of time. If Chevy is going to be firm in their reason for denying the warranty claim, at least that gives you stronger evidence against Grease Monkey. If neither steps up to the plate to cover the repair costs, then I suspect an attorney will suggest you sue them both, join the cases, and then have them fight it out between them. You just gotta hope they don't both point the figure at you and claim you abused the car and say thats what caused the failure.

It's a mess for sure, but all hope isn't lost here. Like I said in an earlier post, my best guess is you'll be out of pocket for the repairs in the short run, but may recover your costs down the line.

 

^^^^^^
And if you win, minus the cost of the attorney that will be more than the settlement. I think you are in a lose, lose situation.

 

"OP, isn't that the sequence of events?"
Yes.

 

I had the same thing happen to me right after a diff fluid change. I took it back and they added the limited slip additive and the problem went away.
If it were me, I would take it to Purifoy and have another diff fluid service done and drive it a while. What's another 100 miles after already driving 1000?
And doing another fluid change is way cheaper than trying to get grease monkey to pay for it and then replacing the diff if this is really the problem.

 

Very simple. Small claims night court. No corporation is sending out a lawyer or representative to night court. I had a tire shop destroy a chrome wheel, and the manager told me to fuuuck off. Ok, no problem. 6 months later I was in night court. Mavis never showed up. Little car owner against a big corporation, and the liberal court system always goes for the little guy.

 

I don’t see how the wrong diff fluid would frag the differential. Is it possible they put motor oil in it the first time ?

 

Problem with that in my area I'd need to hire a bailiff to get money because even with a judgment they can just ignore it. I heard it's a minimum 800$ for a bailiff.

 

So, some updates:

Chevy has replaced my diff. They saved fluid from the rear end and from what is supposed to be in (ie: the brand new fluid they just put in).
The Stingray (base model) takes AC Delco "Dexron LS Gear Oil 75W-90" *contains limited slip friction modifier* (part numbers 10-4034/88862624)
The fluid that was saved is significantly thicker than this. This is BG Heavy Duty Gear oil 75W-140 (with no limited slip additive). According to Chevy's BG representative, this is NOT the correct fluid that should have gone into the vehicle. Since I now have a sample of both fluids, in separate clear bottles, you can visually compare the thicknesses of the fluids. The BG *IS* significantly thicker. It sloshes slower. It drains off of the walls of the bottle slower. it continues coating the bottle for much longer. and on and on.
At this point, both Chevy and BG are pointing to Grease Monkey for putting the wrong/thicker fluid in. I have not yet heard back from the owner of the grease monkey, but when I spoke to him last week, he said he was willing to see any and all evidence and not just dismiss me... Hopefully he keeps his word and I get reimbursed quickly. It seems like he, BG, and Chevy have all been curious what the actual cause is. I know no one wants to pay for a mistake, but it does not (at this point) seem like he is going to leave me holding the bag. He seemed genuinely concerned and interested. I guess we will see over the next few days what happens. Im also curious if I mention about needing a rental during the time if he will also reimburse that, but I guess we will see. Honestly I would be 100% okay with just the vehicle repair being covered. But if i can get the rental time covered too..? cant hurt to check, right? IDK if I wanna push my luck on that though. I think if we can sort the repairs with no difficulty, I wont go after the rental. But if i have to get lawyers involved, might as well through the whole book, you know?

On a plus side, chevy got the vehicle done 4 days earlier than expected. Go dealership! (im sure thats the first actual praise of a dealership ever, hahahaha)

 

Glad your car was fixed ahead of schedule!

I think you want to figure out who, if anyone, is going to cover the repair before you worry about rental costs. Sure, if you end up in court, seek recovery for everything...but I wouldn't get ahead of myself just yet, and if Grease Monkey offers to cover the repair, maybe you call the rental a wash.

Let us know how it turns out.

 

That great. Over the last few years, differentials have been long lead items. Glad to hear they got your quickly. Let is know how it goes, and remember to go easy and keep your speed down for that diff’s first 500 miles.

I’m almost afraid to bring this part up - but you should change the diff fluid after approx 1,000 miles (or maybe a little more) Just be careful where you take it

 

I hope you get refunded.