Just wanted to see if anyone has had a similar experience. I did do a little searching but well 'rear end shudder' and 'rear end shake' did not really give me much to go on.

Anyway, this has happened 2 times in the last couple of days. I go to step on the gas and I don't get much of anything (feels like turbo lag, and it may have been at the time, I don't recall the rpm's I was at). Well then it feels like the turbo kicks in and the rear end feels like it is losing traction and jumping. Inside the cabin there is a definite sensation of a jumping shake and a thumping noise. (Somewhat feels like launching the car)

Now, I don't know if I have just done something wrong to cause it but I've never really felt that kind of shaking from the rear except when launching at auto-x's.

Some background, the car doesn't have a ton of power mods, basically intake, exhaust, reflash. It does have an ACT clutch which I incorrectly purchased and got a solid unspring 4 puc and that has been in for the last 2 years. In those 2 years I've probably put in 10k miles, and around 24 auto-x events with around 6 runs each so I'd say about 140 2-step launches (I am letting out the clutch slowly till it engages and the car starts to roll then releasing quickly to launch, not just dumping it).

So my question is this: Is it just something that I did wrong the last day or two to get my car to do this, or is it signs of something in the drivetrain nearing the end of its life, or something completely different? Any help (or links to a post that someone else made) would be greatly appreciated.