triguy450

I did read the lengthy checklist that ujtruck posted. 99 K3500, crew cab, diesel dually. I seized the motor 2 years ago because the clip holding the oil cooler line into the motor broke, sending all oil out of the engine. the truck sat for 2 years until I could gather the money to find a new motor and install it. I did replace the rod that sticks out of the transmission and secures thru the neutral safety switch. I replaced the fluid and the filter while I was at it. I did put synthetic fluid in it because the auto parts store did not have non synthetic fluid available. My plan was to drive it to a transmission repair station, flush the entire system and replace the fluid again. 5 miles away. I started the engine this week. After a thorough warm up, I put it into drive and the transmission made a lot of noise. I went thru all the gears. 1 & 2 and neutral were quiet. 3, drive and reverse were noisy. I placed it back in park, the noise continued until I turned off the engine. I restarted the engine and the noise went away. I put the transmission back into drive and tried to move the truck. It wouldn't move. I tried reverse, it did not move. I tried the remaining gears, it would not move. Anyone have any theories which direction to take next? I am considering a flat bed to the transmission place to have it looked at. Thank you Ed