My TJ 6-speed NSG370 transmission is kind of noisy when shifting in lower gears, and shifts rough from 1st to 2nd to 3rd. Beyond 3rd there is no roughness. This only happens when in motion. Parked I can shift through all the gears w/o any noise or roughness. A few "car guys" at work have told me I need to replace the transmission fluid but they can't seem to tell me how to do it on anything other than a Civic, and I can't find any how-to info on the web for the manual trans. I've looked at the diagrams in the owner's manual but I can't seem to locate anything that looks even remotely like the drawing. Can someone point me in the right direction?