Is the (rear) differential fluid replacement needed for FWD cars? Is there such a thing as front differential fluid? I can't seem to find answers by googling..

 

On FWD cars its part of the transmission package (transaxle) not a separate unit like the rear differential. It runs on the transmissions fluid.

True 4X4's like the FORD Ranger & CJ Jeeps do have a front differential. The are serviced with the same oil as the rear one. On Jeeps the pumpkin is pretty easy to see, looks just like the one on the rear axle.