Howdy! I just took my 84 Z28 on a short trip (200 miles) and when I got there I noticed my gears were whining. The whine gets higher in pitch as the rpm goes up and drops when you hit the clutch to shift. I checked the plug on the side of the tranny and it's full of fluid. When you take the transmission out of gear you can hear an odd "rumble" from underneath the car. Could this be a bad pilot bearing or is it tranny related. Another thing to note is that it's noisy in 1st, 2nd, 3rd, and 5th , but not 4th ?! Watcha think?

 

Mine does the same thing. Try to change the fluid in it... that's what I'll do. 4th is like a "direct" connection from the engine to the driveshaft.... so it wont make noise like all other gears.

 

Mine did that too...it was the rearmost bearing surface on the countershaft had become pitted. Cost me about $300 Cdn for a new shaft and bearing; put them in myself so I saved on labour big-time.
If you've never had one apart, they are kinda tricky to dis-assemble. In order to get the correct replacement shaft, you'll need to do a 'tooth count' of each gear on the countershaft itself. There are over 30 different combinations; it's not a 'one-size-fits-all' deal.

Good luck with it; get a professional opinion first before digging in; most trans places will do a 'road test' of the car for free.

Pete