so it is not loosing its prime. Thats a good thing! Its odd that it doesn't slip in low gear going forward as they share the same drum only it spins the planetarys the opposite direction. If it was mine I would pull the pan and check the band adjustment. Replace the fluid and filter also while you are there. I had a 2003 or 2004 Dakota my neighbor brought me. He drove it in. Had me fix a few things and wanted the trans serviced. I pulled the pan off and the band material looked like a big rats nest in the pan. I was totally shocked that it still drove and shifted as it should.Birdtracker