bump sorry to bump a old thread but i was wondering ive got a similar problem in a C210 skyline same motor as a 240Z now im a poor school student not 1 cent etc , and ive been getting a grinding sound my car is a auto 3 speed but im not to sure what gear it happens in but ive been babying it lately and ive been getting this grinding sound time to time not always probably about 3 - 5 times in a 20min drive, when i bought the car i had a mechanic drive it and inspect it and he said a uni joint or 2 is on the way out and a gear box mount , so was wondering is it possible for a uni joint to cause grinding sounds ? please god dont be my gear box bearings / gear set the gears shift perfectly and do not slip etc only problem is when going from P to D it makes a clunk but meh and believe its the gear box mount making that sound , lately ive been feeling a bit of vibrations from the gear shifter but not to bad so i just prey its the gear box mount stuffing up more