I have a 2001 Isuzu Trooper 3.5, I love the truck despite constant EGR and IMG issues. A couple of days ago when we received our first real cold front in Indiana something new developed. When the tranny shifts from 3rd to 4th at approx 40mph, I hear a clunk and then I hear another clunk and shudder as it hits 50mph, sometimes this is accompanied by a quick grinding noise. I have disassembled and cleaned the range sensor and it hasn't seemed to help and when I check the fluid I am getting a trickle. I have not dropped the pan or done a partial fluid/filter/gasket change and I'm not getting any trouble codes. Has anyone else experienced this or can anyone advise of a possible fix. It's parked until I can figure out what's going on. Any help would be greatly appreciated.