GTV 2000 transmission noise

[robh]

G'day. Has anyone had this problem?
1980 Alfetta GTV 2000 Has an irregular rattle which seems to be coming from front of gearbox area, have come across one other alfetta doing the same thing.
Is sounds a little like a thrust bearing but is noisy with clutch released and dissapears when clutch is depressed!
Thought the thrust bearing might be a little loose on shaft or lever and rattling there so pulled it all down, went through all donuts and centring bushes, replaced neccessary and greased everything else. Checked centre prop shaft bearing, OK,
Thrust bearing was fine, whacked a new one in anyway, thrust actuating lever all good, clutch input shaft bearings were good, cleaned up and repacked. Replaced clutch with good tight second hand unit, checking all splines, rivets, etc and sure enough still noisy.
The noise has been there since putting on the road five years and over 180,000km ago, (even towing trailers! shame oh shame!!) seems to be getting a little worse but hard to tell for sure.
Cant be too important or something would have failed by now. The noise is intermittently louder then quieter but never quite goes away.
Would appreciate any suggestions. Ps does anyone have a known good transmission to save me downtime? (longer driveshafts, short spacers)

[greengtv8]

First thought was clutch housing bearings...however seen as you've checked that and checked/replaced everything between the two flywheels, i'd almost suggest gearbox input shaft bearings/or a mark on the shaft which the bearing runs on. However, if you throw another g/box in while you look at this one(keeping the clutch and clutch housing the same) it will atleast tell you if it's in the g/box or not! I have come across this when rebuilding these g/box's...not common, but i have seen it.

[meizhak]

Does it make this noise whilst driving or only at idle?

mine has a fair amount of rollover noise coming from it, which will dissapear when clutch depressed

Noise comes from gears meshing at slow speed, could it be this?

meizhak

[robh]

Thanks gents, Had suspected g'box input bearing but kind of wishfully eliminated that because of trouble free mileage, would have expeced failure by now (although mark on the shaft is possible.)
Yes, noise only at idle so low speed meshing sound feasable, getting up to very high mileage and syncro isnt what it used to be so time to start planning g'box rebuild!
Feel more confident it's not going to turn into a box of shrapnel at 120kph though so many thanks!