I believe I have a tracked a mild rumbling rotating bearing sound down to my gearbox. With the engine running and the car stationary there is a rumbling noise which disappears when you put your foot on the clutch. Is this normal?

In these circumstances (foot on clutch & stationary) the gearbox is not being driven by the engine or the forward motion of the car. When I ran the engine with the gearbox removed the noise was no longer present. When I turned the gearbox over manually (by rotating the splined clutch receptacle) it all felt very smooth but there is clearly a rotating bearing sound, it is a rebuilt close ration 4 speed (syncromesh on 2-3-4).

I am not certain what is normal. I am relieved that it does not appear to be engine bearing!

The fact that your rumbling vanishes when you press the clutch could indicate a loose flywheel?

I think you flywheel may be loose.

Edit: I agree with Malcolm!!

Thanks for the reply - that was my first thought/concern. With the engine running I pushed a stick carefully up against the centre of the clutch shaft and there was no change in the tone of the engine. The rumbling was not present with or without the stick! The engine has just been professionally and carefully restored.

Go to your nearest Motor Factors and buy a stephoscope. Use it around the gearbox
with the engine running to isolate source of rumble. As a cheaper alternative, a length os 3/8" wooden dowling, will also work.

Location: s.wales

I hate to disagree with my esteemed colleges, but as the engine is quiet with the gearbox removed I would think we can eliminate a loose flywheel. How bad is the noise? I am not saying that there is nothing wrong with the bearings but in my experience a seven gearbox will always make a little noise when spinning. What is it like under load?

Location: Auckland NZ

With most Sevens you are very exposed to any gearbox noise. Other cars do not sound too wonderful with the floor out.
It is common for the bore of the input gear to be ridged parallel to the axis. If the original roller bearing is used this may be the problem. Not sure to what extent it shows up driving as drowned by gear noise. Possibly detectable externally on the bench by forcing the mainshft down whilst turning the input in gear. Whether or not worth worrying about I dunno; many cars run/ran with.

Location: Auckland, NZ

Last year I convinced myself that the bearings in my rebuilt gearbox were rumbling and it turned out to be the rivets on the clutch driven plate that were loose. Worth checking whilst the engine and gearbox are separated.

Peter,

This noise isn't related to our earlier discussion on clutch fingers and throw-out bearing is it?

Tony.

Location: Malvern, Melbourne, Australia.

I have the same problem as Peter, same gearbox - it was rebuilt with new close ratio (Nippy) 4 speed gears (syncromesh on 2-3-4) - but I would not describe the rumbling as mild, at tickover the gearbox is much noisier than the engine.

I replaced the gearbox with another while it was rebuilt, again, and the problem disappeared so I do not think there is a problem with the engine, flywheel or clutch. When the original gearbox, which had been rebuilt with all new bearings was put back the problem returned.

I now have an original Nippy gearbox which I will fit when I get time but it would be nice to get to the bottom of the problem so any ideas as to what to look for would be appreciated.

Hi Everyone

thanks for all of your replies - it has been most helpful to someone who isn't very experienced like me.

It is difficult to characterise the gearbox noise volume.

To someone who is mechanically minded it is quite noticeable, to someone who isn't they might not even notice it. It only becomes apparent when the noise stops when pushing the clutch. I hadn't noticed it myself until I finally got round to finishing the accelerator linkage and making the car driveable (minus wings seats etc!).

The noise is less noticeable than say a noisy (higher pitched wizy) thrust bearing. However the car (2 seat AEW) currently has loose bare metal floors, no propshaft cover so any noise is going reverberate.

Peter, whereabouts in the country are you? You may be able to enlist some advice from a local clubmember

Location: Farnham

Hi David

I live in Walderslade Chatham, Kent. I will contact the local group.

I have spoken to the person who rebuilt my engine. It came out in the discussion that my professionally rebuilt gearbox has been fitted with new close ratio gears and it looks highly probable that the noise could be due to that. Apparently when new close ration gears are installed they take a couple of hundred miles or so to bed in.