Does a TCM have to be bolted down to effect a ground condition, or is to ok to "just be there" with the cables plugged in under the floor bracket?

 

I don't believe it being unbolted will affect how the TCM operates, but it is best to have it grounded to the chassis to prevent any possible damage from a voltage spike that could damaged an ungrounded control unit. If you must drive around with it unbolted/unsecure, use a jumper cable with alligator clips for an easy bonding of the case.