the flywheel and bellhousing is bigger on a tII. make sure if youre starting with a s4 to put an s4 engine in it. and if you have an s5 put an s5 in it yadda yadda yadda. i tried to put a s5 tII in a s4 n/a, got pissed off, sold the s5 and bought a s4 tII.