It sounds like you have a bad spot on the ring gear like hotrod describes. Inspect the ring gear like he describes I am assuming you are talking about the 48 model in your profile. If it is the ring gear, the only way to fix it is to pull the transmission, clutch and flywheel. If the back side of the ring gear looks good, you can heat it to where you can remove it and flip it around and shrink it back on. If its already been flipped, you will need another ring gear.
