Drivetrain Thunking - SPF

[MidOHasp]

Any SPF owners experience this?

Pulling in and out of driveway, real low speed stuff, if things start to "buck" a little bit, there's a thunking noise in the tuneel toward the rear of the car.

Last night, was letting a buddy test drive and I assumed that he respected the whole 500HP, 2500 pound relationship. He was immediately sideways with an oncoming car, and I think he got a little nervous... Basically shut it down and turned into a development off the road he was on. Pretty sure in a fit of panic he grabbed 5th gear and was going about 10 miles per hour. The bucking was violent and so was the noise.

I think he was so scared he broke it he couldn't find first gear. I kept telling him to keep the revs up and find first gear and he'd be ok, but I really thought something was wrong.

We got back the 1/4 mile to his driveway and I took it out for a spin. Everything was fine.

I'd noticed the thunking occasionally before, perhaps the new park brake setup they're using, but had never heard it this violently before. Now it raises the question...is this normal?

Setup:

SPF 1670 (new diff mounted hand brake)
351W
Tremec 3550

Thanks guys...
JP