Hey fellas. i have an 88 firebird 2.8 v6 and i was driving down my street today and i put it in first because its the 5 speed, and my shifter started bobbing up and down a good 2 inches or so. it did the same in second, and third, but in third it just vibrated too. also, my speedometer just **** the bed too so it wont read how fast im going. any help would be greatly appreciated. email would be easiest, but any way you can contact me is good. my email is firebirddude88@yahoo.com thanks a bunch guys.

 

Sounds like your tranny mount went bad, one of those years they changed the design of the mount,the replacement oem style is expensive. If yours is like that, you can use a mount & crossmember from a th700r4 equipped f body. Do some junkyard hunting.
First see what a replacement costs.
Maybe your cable loosened up.

 

Yes, it sounds like your transmission may be trying to come through the floor and drop on by a visit, a bang every time you accelerate will more or less confirm this, but I really don't see any other thing that could cause what you describe.