1300fwd gearbox knocking at certain rev range

[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 1^st gear, then stops when changing to 2^nd gear until reaching about 25 mph, then stops when changing to 3^rd until about 40 mph, then stops when changing to 4^th 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.

[RobPearce]

It could be any of a number of things.

If it's a rattle then it might be as simple as a loose cover plate on the clutch access, which resonates at those revs.

If it's more of a knock - how fast is the knock? How loud?

[epcot_pete]

Thanks for the reply Rob.

In hindsight, I should have mentioned that I overhauled the gearbox about 4 years ago and replaced the syncro rings, some bearings and a new stronger design of input shaft with matching gear (the shaft that goes takes the drive from the clutch to the gearbox gear train).

The knock/rattle has got slightly worse over time and difficult to describe loudness. I know its there as I use it as when to change gear, so I suppose quite noisy and I don't have a radio.

Hope this helps

Many Thanks

Pete