1997 F250 7.3l Flywheel

[mistymay]

I Need Your Help!!!
While Driving Down The Road, The Truck Started To Shimmy While Going 75 Mph. Slowed Down To 50mph And Got It Home. Thought It Was The Throw Out Bearing, It Was Out And Replaced It. The Truck Is Still Doing The Same Thing. Can't Get It Over 35 Mph, It Shimmyed So Bad That It Vibrated The Starter And Transmission Bolts Loose..... Is This A Flywheel Or Do You Think It Is A Fan Out, Or Maybe The Clutch?

Now It Wont Start At All.

Can Anyone Help, A Flywheel Is 1,000.00 And Want To Make Sure It Is What I Think It Is.