knock in the floor board
 

sometimes, but not always, when i let the clutch out in first, or change gears, there is a knock that i can feel in the floor board. And when i did a burnout for some friends a couple of days ago i felt it knock repeatedly until i let off the gas. Im hoping that at the most it is a clutch problem but want to find it before it grows into something worse. what do you guys think?

I'd look at the trans crossmember bushings (could be trashed rubber or the actual crossmember, the metal around the bushings in my 86 GT rusted out pretty bad) and the engine mounts. We just installed a set of BBK equal lengths in my friends (my old car) 86, they fit tight and rub the steering shaft and hit the frame on the passenger side. His motor mounts are pretty smoked, anthough the headers could be made to fit slightly better :mad: . I'd also go around and make sure any bolts/mounts are tight too.

well as i drove the car more i noticed that it doesnt happen as i change gears but as i push and let off the gas. Could this still be the transmission bushings or loose bolts?

That'd be the first place I'd check....

I had the same problem....my crossmember bolts were loose from the factory...check them.

I just wanted to say that you guys were dead on about the problem being the crossmember....took me a while to get around to it but just bought a brand new one. I love this site!!

my 86 GT had the same problem, i just recently replaced the crossmember. seems to be common with these cars.

Do you have a h-pipe in your Mustang? If you do check to see if it's your h-pipe hitting the underside. I know I had the same issue and I put a piece of heat resistant rubber in between and problem solved.