I unfortunately ran over a small chunk of concrete that I did no see coming off an off ramp of a freeway. The chunk of concrete hit the transmission pan and continued the length of the car.
The transmission was left with only one gear, 3rd.

The car was flatbed to a Mini dealer for service, they repaired it, but it now disengages randomly completely and when and if it reengages it does with a thump into 3rd gear only or I have to turn off the car and restart and all is well again.

I was told that the Steptronic six speed transmission in my 2005 Mini Cooper S is not repairable and should only replaced, is this correct?

 

This should be covered under your comprehensive insurance, since it happened while driving. Make it a point to tell the dealer that you think the transmission should be replaced. I would be surprised if they give you quibbles over that =).

 

Steptronics (non-CVT) autos are very repairable, but as with most all major drivetrain components, if the damage is significant, replacement might be the best option.

 

You can buy my wife's 05 and have the trans with it