1300 fwd 1966 gearbox knocking

[epcot_pete]

Could someone please advise me on a gearbox problem with my 1966 1300 front wheel drive.
The car drives well, starts first time and has no other mechanical problems.
It relates to a mechanical knocking/rattling noise in the gearbox, but only occurs at certain rev range and at no other time.
The knocking approximately starts at 15 mph in 1st gear, then stops when changing to 2nd gear until reaching about 25 mph, then stops when changing to 3rd until about 40 mph, then stops when changing to 4th until about 55 mph when it starts again. When cruising on the flat or going downhill at 55 mph the knocking goes away, but appears again when accelerating or going up a hill. It tends to go away at 70 mph, not that I usually travel at that speed!
So the mechanical knock/rattle occurs through all gears at a certain rev range – has anyone got ideas please?
Thank You.
Pete

[tony g]

Ive never looked at one of those boxes but it sounds like input shaft speed related to me. Are there drop gears after the input shaft? Could be a bearing on its way out maybe. Bruce may know a lot more I expect.

Tony

[dollyman]

Possibly drive shaft related and transmitting the noise so it sounds as though coming from the box??

Tony.

[Carledo]

I agree with Tony, its rev related so anything after the gearbox output shaft to the diff can be eliminated. It's there in 4th gear, so that lets out the laygear cluster. Your problem logically lies in the transfer gearset between the clutch quillshaft and the gearbox input shaft.

The only good thing about this, is that that geartrain is accessible through the tunnel in the car, without removing the engine or gearbox!

Steve

[Triumph1300]

Input shaft bearing, clutch tube loose, or clutch cover plate issue would be my first thoughts.
Have you taken the clutch cover plate off, and had a look?

[epcot_pete]

Thanks Lads for reply's.
In hindsight, I stripped gearbox about 4 years ago and replaced syncro rings, some bearings and new, stronger design input shaft and gear that goes through clutch and top gear of gearbox. Do you think this may be the problem?
Many thanks again.
Pete

[Triumph1300]

Does it make the noise when revved stationary?

If so, stethoscope time, find exactly where it's coming from