Yes, I realize that. But what exactly is a 4wd transmission? I've never heard of one. A 4wd is a regular tranny with a transfer case behind it. And if it has the wrong tranny in the truck, how exactly does that happen? Sure, mistakes happen, but that seems a little out of the ordinary, don't you think?
Nice truck btw.
As you noted typically a modern (1980's up) domestic 4WD automatic transmission will be a standard 2WD automatic transmission for that specific vehicle with a different rear output shaft installed in the transmission and 4WD rear tail shaft housing installed that allows for the transfer case to bolt up directly to the rear of the transmission. This also can also sometimes require a different rear transmission cross member and mounting location for the rear transmission cross member due to the different 4WD rear transmission tail shaft housing installed on the now 4WD automatic transmission combination that may be longer in length.
With this conversion you now have a "4WD Automatic Transmission".
You will find similar conversions on Manual Transmission conversion from 2WD to 4WD configurations.
In each "case" the addition of the transfer case to the transmission will also require a different driveshaft for the 4WD application versus the 2WD application.
In the ad the seller comments about both the "4WD transmission and the rear crossmember/driveshaft. One can only surmise that they have a installed a trasmission set up for 4WD with a transfer case attached OR a transmission for a 4WD and have not converted back to 2WD configuration. Another thought is that they were trying to update the transmission with an overdrive transmission as these Centurion vans of this era all had a 3 speed C6 automatic transmission. I am sure a call to the seller will "Tell The Tale"!
Either way it sounds like a MESS and this van is vastly overpriced with this transmission issue whatever it is as there are not a lot of folks beating down the door to buy and old "Centurion" Van!
Now with a COMPLETE 4WD conversion a Centurion Van would certainly be neat and a conversation piece HOWEVER not something "I" would want to use "Off Road"!