engine shutter

There is a shutter when going 30-40 and around 50-60. Anyone know what this is?

It would HELP A LOT to know the year, model, engine, and transmission.

1995, thunderbird lx, 4.6 V8

How many miles on the car? I had a 95 4.6 V8 Cougar that did the same thing. Does it do it on acceleration or cruising on up shifts? Could be one of two things. Mine had both problems back to back. First it was cruising on up shifts, changed the trans fluid and filter and it took car eof it. Not long after it was on acceleration/ up shifts, changed the plug wires and it went away. I had about 38K miles on the car at the time.
Just my 2 cents

Flush your tranny and tc and install mercon 5. That should do it.

you might want to check your timeing also, i had to same problem, my car jumped time on me one day while i was driving

Flush your tranny and tc and install mercon 5. That should do it.

I 2nd that !!!!

But watch out for missfire too...:

If it's a 95 you will be able to check timing but not adjust it.
DIS ignition.