I have 94 Z28 with an automatic. My problem is when im at a complete stop and when i give the pedal a good amount pressure, right under shifter my transmission make like a large thump sound from 1st gear. One guy said it could solenoid in transmission. Now if i ease into the pedal it wont make the noise.
PLEASEEEEE HELP!!!

 

Not an uncommon thing. If your trans mount is torn, the tail of the trans will lift and smack the tunnel. Check your mount by lightly lifting the back of the trans with a jack. Throw a 2x4 or 6 across the pan, then lift with the jack. If the mount is torn, you'll see it split apart.

 

^^^ agree its the transmission mount. mount is about 15 bucks and a very easy job
you can see the mount between the crossmember and the transmission

 

Thanks I took it to a gm mechanic and he showed me that was the exact problem! It's was completely broken.