Yes, I have a question. I have a 2007 Trailblazer SS. I went to Valvoline to get rear end fluid changed and asked them if their limited slip additive was under GM specs. He said yes. It didn’t start howling right away. It took 2 days. They put a 4oz bottle of limited slip in it with the fluid change, but they were supposed to put eight.
So I when brought it back, they sucked some fluid out and put 4 more oz in it and said drive it 2 to 3 days and that it should quiet down. But it didn’t, so they said bring it back. We will drain it and fill it again to see if this fixes the problem. So I drove it two more days, but it didn’t.
I went to GM. They drained it, cleaned it out and put some new fluid that already has the additive in it. It stopped, just like that. It only had 65000 miles on it.
Well, now it started howling and it’s getting worse. So I think that the additive they used prematurely wore out the clutches in the rear end causing them to go out. We don’t tow with it, and my wife is a soccer mom.
What are your thoughts? It has a clutch style posi rear end where the additive lubes in between the clutches for less friction. So, if the additive is wrong, it will have more friction causing it to chatter and make noise in the end wearing them faster. We probably drove 300 miles.
It’s impossible to say without knowing what the (apparently) fast lube facility put in there. The fact they were telling you to drive it to see if the problem went away pretty much says they don’t know what they’re talking about or they know full well and are simply giving you the brush-off treatment.
If the rear axle has now gone to lunch I’d say that whatever they put in there was the cause of the problem. The only thing that nags me is that I’m having a hard time seeing an out of spec fluid causing an immediate howl in the rear axle. A no oil at all situation could cause this but you say they drained and refilled it so I’ll omit that possibility.
You also state that you went to this facility to get the rear axle fluid changed. Since most people don’t do this or even think about the process this brings up the scenario of a pre-existing problem and someone looking for a place to point the finger.
No doubt you’re upset with me over the inference there but I’m not saying that you’re guilty of this; only that it’s a common practice.
So why did you decide to go get the rear axle fluid changed?
They are to blame. I’d bet a look-see at the ring and pinion gears would be “telling”.
My guess is that they put something too thin in, diluting the lubricant. The actual contact surfaces at any given moment between the gear teeth is very small, and the load very large. The lubricant must be thick enough to hold up between the gear tooth surfaces under the pressure involved. My guess is that the howling was the sound of essentially metal on metal in the mesh between the gear tooth surfaces.
Sorry to hear of your experience. A good failure analysis of the gear teeth with good microphotography combined with a good lawyer might get you some justice. Meanwhile, GM having drained the differential and refilled with the correct fluid might buy you some time. Emphasis on both sentences in on the word “might”.