Most of the Ford uppers have an email address, ie wford@ford.com. These may be available on blueovalnews site. Get someones attention and ask personally for Bill Franco to check out your car. Bill is no longer on the mustang program, but on some international job. If they say he is not available ask for someone of his recommendation or caliber. Bill used a vibration tester to determine where the vib was coming from. The unit (available from Ford for dealers)gave a readout of the frequencies of the vibrations. Bill could tell by the range of the harmonics which drive line part was creating the vib. We made about 4 or 5 road trips to index my driveshaft. Bill was a very personable, knowledgable, professional gentleman. I should have my tail kicked for not writing Ford and telling them the same. If you cannot get Ford to go along with any of this or a trans SWAP that cures the problem it would be LEMON LAW for me. This sounds like a blueprint of the 99 vibs. A new driveshaft and the factory index will not necessarily eliminate the driveshaft as at fault. My run out on my driveshaft is .030 " on the axle end. This is offset by any runout on the other end, the pinion flange, the output shaft or pinion shaft.
I would not be happy with the trans if the dealer has had it apart. Again, new trans, no vib or Lemon.
I am not a ford tech but I am a gm tech and it works the same for us we can not just put a tranny or motor for thatmatter in with out tearing down and doing a cost analysis.It sucks being a tech in some cases cause we have our lift tied up for sometimes a few days.I can only imagine your frustration.I read a thread on svt performance about a guy who had a motor go bad in about 1000 miles and wound up having to go to court to get it setteld when it was a manufacturing defect cause the tech building the motor forgot to put a c-clip on the wrist pin.Appearantly ford is worse then gm in this manner either that or its the dealer.But it sounds to me being a tech that if the vibration is only in 6th gear it would almost have to be something in the tranny especiall if its getting worse after they tore it down it should be cut and dry for them to diagnose.I have rebuilt t5's but never a t56 but tomarrow I am going to pick up one of out firebird books and look at it abd see if I can see anything that might cause a problem in sixth gear.
Well they offered to pay my car payment for the downtime (1 month) and the transmission finally came in and will be installed tomarrow so I should know by Friday weather i stay part of the cobra club or buy a vette after the lemon law to spite ford....maybe even an SRT