My 2008 Dodge Ram with automatic transmission has no gears at all but engages back into park. No warning signs of issues, no hard shifts, no slipping, no stalling, no limp mode, and simply was fine one minute then 10 minutes after I was in the store there was no gear like it was all neutral except park. Any ideas so I don't start replacing parts that are over $300 parts for nothing? I was told TCM but I have none of the warning signs at all it just was good 1 minute then I shut it off and was not good 10 minutes later when I started it back up.