Hey. I just finished my swap of an 89 5.0 mustang motor into my 74 datsun 240z and I do believe it has a world class tranny although I bought it from a guy on cl and you know how that goes. However I digress, I believe its gone bad or about to go bad really fast I cant tell but I believe its making a noise in gear kinda like a "tat tat tat tat" Its been popping out of first gear every now and then and when I go to shift really fast when stepping on it the gears grind like a mother ****. The "tat" noise never happened until just a few days ago. I down shift alot i dont know if it has caused it. But its loud not loud enough to hear while driving because the side pipes on the datsun make it hard to hear but I can hear it when I put the car on jack stands and start the car and put it into gear. I do also have a differential problem being that it makes a little click when i rotate the tires. Another thing I noticed is when using a stethoscope I could hear the noise in the rear end and the tranny.HOWEVER when looking and hearing closely I noticed that the noise is louder in the rear of the tranny then the diff. Also The noise is almost perfectly synced up with an output shaft wobble that you can almost not notice unless you just lay there looking and listening. The wobble is not in the rear end as I just made a solid diff mount for the rear end and the dif does not move at all during any acceleration including the input shaft on the diff. No shaking once so ever.