could any one give me some advice on why my cobra will not go into rev. all the other gears seem to be o.k no grinding hanging,clutch has no noise is still very firm i replaced the trans.mount and checked the motor mounts they are bad but have not been replaced as of yet.any one got any ideas?  

unlike foward gears reverse should be engaged by a sliding idler gear...could be broken, binding...something..probally have to tear it down  

Sounds like something's definitely up internally. Have you tried putting it in reverse with the car turned off, then starting the car to see what happens?

If the motor mounts are bad, and the tranny mount was bad, the torquing and bucking of the engine/trans assembly could have caused some damage.