three speed tremec transmission noise

[2tone4by]

hey guys! got this 78 4 wheel drive chevy with a three speed on the column.....only one I  have ever seen in a 4 wheel drive. It makes a noise.....kinda rattling sound when sitting at idle in. neutral. it makes this same noise in first and second gear, but the noise quits when shifted to third. Also when idling in neutral and making the noise, it will stop making the noise when the clutch is pushed down.....anyone got any ideas what may be wrong....thanks a bunch

[dvdswan]

sounds like a throwout bearing going south.  especially because it goes away when you push the clutch in.   now with the no noise in 3rd, but in 1st and 2nd.  well, 3rd I believe is the mainshaft gear or straight through gear so you may have issues with one of the 2ndary shaft bearings as well. 

either way the trans needs to come out for inspection of both.  but 1st thought is the t/out bearing.