I want to thank all of those that gave me advice on supporting the engine and rear end for a split on my 3600. I shimmed the front axle, blocked both front wheels, used two floor jacks and rolled it backwards. Worked well.
I found a pin and 2 washers in the bottom of the bell housing. The pin and washers came from one of the three lever arms the throwout bearing engages to activate the clutch. Basically a hinge pin. The small cotter pin that holds it in place had sheared off.
I put the pin and washers back in place with a new cotter pin, and hope my problem is solved. Bolted the halves back together. The clutch was installed 6-7 years ago. Looks very good externally.
Has anyone else had this particular problem??