well it sounds to me like you just plain and simply missed third and it dosn't sound to me like you shifted into first either. i test drove an lt-1 stick this past fall and i got on it and when i shifted into third i let the clutch out just a little bit too early and it made a loud bang, shook the car up and down like i ran over a land mine, and it also popped the console up. after i stopped and popped the console back in and examined the underneath of the car to make sure the tranny was still there, i drove it back to the dealership and i got on it again and to my surprise it didn't seem to hurt the car at all. and just so you all know i didn't accidently shift from 2nd to 1st i just let the clutch out to soon.

 

lt1's seem to be stronger. my best friend had one and he did it to his and nothing happened. i do it to my ls1 and sure enough...

if you have a messed up idle you probably bent a valve, check your pushrods first. you do not want to replace valves. it will get a lot more expensive than pushrods.

z top: you musta put it into first or else all you woulda done is grind the gear, which would not shake the car. if your car is shaking you mis-shifted. trust me ive done both good description of it as that is what it was like. hehe

 

The exact same thing happened to me only I floored(my v6) the gas to get on it.And when I went to let off NOT the sucka kept going.I slapped the pedal with my foot .Like the linkage stuck or something didnt work.Had to go to "N" and rev limited it for a bit till I figured it was the mat. Needles to say I dont use a driver floor mat in either car,what a trip and it did tick me off I had only had it for a week 12K miles on the clock.
They should put a warning on those mats

 

When I had my TA, one time I got a loud popping sound while releasing the clutch pedal like a piece of plastic breaking or something, i wasn't racing, in fact i was drving slowly, didn't change the car at all but it was weird

LOL, I thought you were driving the mustang when this happened.

 

This I can relate to. I tried to shirft into 3rd from second after lighting the tires up, but started to shift a milli second before I had engaged the clutch. Same loud thunk. I didn't notice any idle trouble so hopefully the internals are still intact. Keep us posted.

 

heh, last night after getting off work I was on the hwy and downshifted to get around some traffic. I hit 2nd instead of forth when I was going 60mph. I was like