Replacing fan on a graphic card (ATI or Nvidia)

Hi

Is it possible to change only the fan on the graphic card in a mac pro 2008?

I have two mac pros, both the same model (2008) one had nvidia card, and the other has ATI card (Radeon HD 2600 XT).

Is it possible to change only the fan, as the bearings of the fans got so loud, that are unbearable to listen to... I changed the nvidia card two years ago because of this problem, but if i could only upgrade the fan and keep the cost down (don't have to buy new graphic card...) it would be great.

thanks for the info