Either the forward clutch failed, or the feed bolts have backed out.
I agree...the first hint of forward clutch distress was the shudder on acceleration.
@trackspeeder knows what he is talking about.
If it went out you wouldn't have reverse either.
@Rdnck84_03 is pretty savvy, too...he is talking about the torque convertor.
If a torque convertor strips the splines, breaks a weld you would not have any motion, either direction. On the other hand, bearings and washers chewing up leads to a slow, horrible death from metal shavings that stop up stuff.
As far as rebuilding the unit yourself...how long can you be without the truck? You only want to do it right the first time and the learning curve is kinda steep if you have never done one before.
Don't get me wrong...I encourage you to tackle it, but I hope you have a good friend to help mentor you along for this one.
The E4OD is a big, beautiful, unit...kinda makes me want to cradle it in my arms and slowly rock it to sleep. I was saying that about that unit 'way before 'big and beautiful' became a catchphrase...sorry....
It IS a magnificent piece of engineering...find you another core unit and take it apart and see what I am talking about.
Anyway...once you decide to fix it...you have to make sure all of the electronics and connections are sound...or else you are going to have trouble.
On the subject of pulling codes...some codes that are generated while you are in motion might be erased when you shut it off...if you want the whole story you need a scan tool or code reader that will give you codes KOEO and KOER. Ford was slow in providing 'live' data until forced to around 1995 or therabouts...so...you might have a little trouble, there.
Keep your head straight and don't give up !! Most of all...don't do this...
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Good luck on it..!!
Take care,
X