I have a 2004 3500 with a 6 speed manual transmission. Replaced the transmission in April with a factory rebuilt transmission through a transmission shop in Salt Lake City Utah. After the first 2000 miles the transmission started to shift hard in the lower gears especialy when the truck is at a dead stop. Transmission under warrantee and took to dealer. He said the shop put in 80 90 oil and this was the problem. Shop said it was 80 90 synthetic which was correct. Can someone tell me what the consequences are of non synthetic in the trans%
