4L60E Flexplate question

[Patch]

Picked up a 1997 4x4 GMC Sierra 1500 on Friday with what was described as a blown transmission. While starting it, the starter made a strange metallic sound and the engine seemed pretty unbalanced. After it warmed up a bit, it smoothened out considerably, and that is when you could start to hear a dragging, slight chirping sound from the transmission area. I put it in reverse...and it made no horrible noises....put it in L1 and same thing. Both times I had directional movement. Drove the truck at a hair above idle about 40 ft. with no issues. Put it in reverse and backed into the driveway space...again with no issues except the accompanying noises. I have not had the opportunity to pull the cover and inspect the flexplate, but I have a gut feeling that is the issue. The seller said this transmission had been rebuilt not long before he bought it.....so I guess we'll see shortly. Any of you ever had a failed flexplate with the same sort of symptoms? (Forgot to mention the previous owner said this all started when he was going down the freeway and the truck would not go past 55-ish mph)