It is your tranny mount, either the bolts are rusted and broke or they are just loose.
or it could also be that your drive shaft became bent but that is very rare unless you drove over something hard enough to bend it.
it could also be that if it only bangs when you shift it into gear that you need tranny fluid or your bands in the tranny could be going.
how to change brake lines on a 1996 ford econoline e-150
If it has one, you simply use the correct size socket and ratchet and turn counterclockwise.
that all depends on what is wrong with it
My econoline from 1994 has the fusebox on the stearingside under the dasboard. And is molded behind the brakepedal
How do you take out a battery from a 95 ford econoline van
R134a
Actually , it's fuel injected , so there is no carburetor on a 1996
No....The engine mounts are in the wrong place.
You need a new gear box (transmission)
There isn't one. A transaxle is a single assembly which combines the transmission and differential, and connects directly to the axles. You'll see this on front-engine, front-wheel-drive cars, or rear engine, rear-wheel-drive cars, but the Econoline is a front engine, rear-wheel-drive vehicle, where the transmission and differential are separate assemblies, connected by the driveshaft.
https://www.fleet.ford.com/maintenance/owners_manuals/default.asp
the transmission that is in a 1996 f150 is a 4r70w if automatic