268k mile tranny moves a little, replacement doesn't budge!

Hi there, I have a 1996 Ford Aerostar with the 4.0L V-6 which ran perfectly up until mile 268,797.1 The van was towed home but still moves itself when the engine is revved very high. Racing the engine I was able to drive it into my garage and replace the transmission and torque converter with a tranny and torque converter from a '96 explorer. With only 87k miles. Well the swap went well with only the only visible difference being an additional plug present in the explorer's tail shaft.

Making sure there is fluid in the torque converter and transmission I start up the van and put it in gear which no response is felt, I leave then van running in drive for about ten minutes but it still doesn't shift go into gear(transmission doesn't physically engage into gear but the column shifter shows transmission is in drive.

I am very stumped right now and am wondering if I missed anything!

btw, the old torque converter makes rattling sounds when shaken as if something inside fell apart.

Any ideas will be greatly appreciated!

Thank You!