Guys and Gals,
There is a TSB for the drum in the trans. Let me be clear. If you're having shifting issues take the car to Ford to have the issue diagnosed and ask about the TSB for the drum.
Take it from me...don't try to let a trashy trans shop fix the issue. They won't even look for any Ford TSB's and they're gonna charge you for a full rebuild($1500 plus). In my case they did this and didn't even replace the drum. Most shops also charge for a "new case" (if needed) but they use a remanned version of something they pulled out of another Focus and NOT a new Ford case. The rebuild I paid for failed after 450 miles and I had to go to Ford anyway.
Start with Ford if you're having trans issues and ask about the drum. I had bang shifting, shuddering/chattering in the 3/4 range both into 4 and downshifting out of 4. I had no issues with 1, 2 or reverse. My trans eventually started to slip since the damaged drum was causing bang shifting and there was fluid in the grooves of the drum. The clutches were burned too. I can even load the pics(see below). The drum had visible grooves worn and the trans cooler was FULL of metal shavings. I now have a remanned Ford trans and learned my lesson the hard way. Remanned trans was $2200 plus $600 installation with a 3 year/36k mile warranty. The trans shops will only do a year warranty. I have A LOT of documentation to show that a well known trans shops near me didn't put the car back as they should have so save yourself the headache.
TAKE YOUR CAR TO THE FORD DEALER! ASK THEM TO ROAD TEST, DIAGNOSE and LOOK FOR TSB's before they pull it apart. There's a lot of discussion here about solenoids and I've read about internal wiring harness issues. Trust me, have the car properly diagnosed!!!