front end shakes badly at 40 miles per hour on 1993 Ford F-350

shakes badly at 40 miles per hour, if i speed up or slow down it stops, all the time

Asked by for the 1993 Ford F-350
If this isn't a dually have the tires rotated and balanced as a out of balance tire will always come in and out of balance at a certain MPH, Then if it persists you've eliminated that possibility and have the tie rods and suspension checked
3 more answers
check the sway bar busshing or the track bar busshings
check your front shocks, it will cause the same thing.
try changing your tirod ending i did that in my dually and it drive fine now if you let it go it will destroy your ball joints