I raced my stang all last season and noticed that towards the end of the season when I accelerate at a low rpm in four gear, under what I would call a high torgue situation, the car a "thumping grinding" noise can be heard from under the car somewhere under the front seats. Ive have put a 4.30 gear, hooker long tube headers and some suspension parts. It only does it when accelerating. There are no visible signs of rubber on the drive shaft and nothing appears to be loose. This used to cause the car to go into failsafe mode un til sct "fixed" the tuner. Anyone got any suggestions? Thanks in advance.

 

Could be the gears, that's the only think I can think of, especially if you're saying that you're hearing a grinding noise. Sounds like what I had with my Motive 3.90 gears.

 

ruh roh. Step 1: delete your post, especially the part about "raced all last season.". Step 2: return to stock. Step 3: Take to ford dealer for warranty repairs.