I have a 1999 Ford F350 Super Duty 6-Speed Transmission.I have a problem with 6th gear snap ring busting when I let off the gas. I just took the transmission out of the truck and replaced the snap ring for the first time. When I put the transmission back in the truck it did not last 2 miles and it done the same thing as it did before. When I put it in 6th gear it is like it is in nuetral. If anyone has any ideas what else might be wrong I would appreciate the feed back. Thanks!