I am currently running a TK500 and love it save for a few "odd" noises. First off, what does the little tag read that is bolted to the front of the transmission?
Don't forget to "index" the bellhousing if you chose the Lakewood. I also bought my TK500 from PBF and it was the very first one they sold. They also installed it and told me to break it in for 500 miles which I did and it nearly killed me!
Now keep in mind my car is stock accept for underdrives and a K&N filter so the car is so quiet you can hardly hear it run. The noise* I do hear isn't the slight gear whine that is "normal" of Tremecs but almost like a bearing gone bad (*=rattling of a sort). Driving it around town I love the way it shifts. I hear a little noise* in second gear for a split second between 1600 and 1900 rpm. I also hear the same noise* except louder in 4th gear between the same rpm. Recently another noise started only in 4th gear that begins at 3 grand and gets louder til about 3300 rpm or so then gradually falls off as the rpm increases to about 5000 rpm.
I called PBF and told them about it and I am supposed to take it over to let them check it out as soon as I have a day off. When I did call, I explained the situation to them and got this response: "I don't mean to sound rude but what in the hell were you doing in 4th gear at that rpm?"
I dismissed the commment and continued the conversation until he told me I should bring it in.
I understand racing or accelerating from 1500-1900 rpm, isn't ideal but cruising, windows up, a/c on in mild traffic, in a 99.9% bone stock M u s t a n g with factory 3.27s should not be any sort of a problem with the tranny riding at that rpm. I don't think it takes a genius to figure that out. Also, the car being that stock and the tranny rated for 500 ft lbs of torque, I don't think I could have broken it either.
The reason I asked about the tag on your tranny is the tag on mine, ( I didn't write down all the numbers/letters) but saw 3550 on it. This made me wonder did I really get the TK500 or a 3550. I know the TK500 replaced the 3550 and has a red shifter (which mine does)and also as the TK600 replaced the TKO so maybe that is why the tag has 3550 on it.
Anyway I would definately pay attention to noises in that tranny. I think that although there is a new name on the trannies and maybe only a little design change, we are the guinee pigs. Wish you well on yours.
I cant wait to get everything put together, hopefully I will be done sometime today. i know the TK-600 is a little overkill for my current combo but i dont wanna ever have to worry about a transmission again. BTW anyone now any specific way i need to break in this transmission ? 
everything finished except for filling it up with syncromesh and taking it off the jackstands, its gonna be hard to go easy on it for the break-in period
