I have an 01 Expedition and had the TC shutter. I read a few posts on here and saw that someone had put some friction modifier in their 01 Ex and it helped. So I went to a ford dealership and bought some friction modifier and put it in, the shutter went away, this was alittle over a month ago. Now it feels like the torque converter is going bad, it stumbles and bucks when taking off and in overdrive sometimes. I changed the fluid and filter Friday night and it didn't seem to help. I used mercron since that's what it said on the dipstick and I've read that mercron v can harm the 4R100 trans. But I just read where adding friction modifier to mercron in a sense makes it mercron v, so did I destroy my trans? Will I be able to install a new torque converter and solve the problem? Thanks for any advice in advance.