980H Transmission Slam

I'm having a slam when i put my 980H into second gear. It doesn't occur with any other gear only second.We drained the oil but there were no cuttings in the oil and when we pulled the transmission the gears and bearings were in good condition with little to no wear. In the magnetic strainer there are large amounts of copper thread like shards. What could these be caused by?

980H Transmission Slam