Change fluid back to non synthetic with a limited slip additive.. It may come back around..
That fluid its just too slick for your clutches to grab correctly...
Well isn't the friction modifier what makes the clutches work correctly? I always thought that if I would run a cheaper oil with nothing in it and it would help.
I coasted after that. My first pass Friday night was an 8.20 and I lifted 3 times then coasted out the back. It just wasn't happening then I found the broke track bar mount.
I'm not sure about a 15" but call them and ask. They aren't bad to deal with. I gave $678 I believe after metal stems and shipping.