Gearbox Whining - Diagnosis?

[Anthony]

Could someone help confirm my gearbox diagnosis please?

 

3 Synchro, Herald 1200 Gearbox:

When idling (or revving) in neutral at a standstill it's silent;

When I pull away, and whilst driving the gearbox begins to whine in all gears;

It's loudest in first gear and gets quieter when moving up through the gears;

It's loudest when under-load and becomes a little quieter when easing off the throttle;

If I depress the clutch and coast along (whilst remaining in gear) the noise disappears;

The noise reappears when the clutch is released;

The whining noise sounds similar to a straight-cut gearbox.

 

I'm thinking it's either the layshaft bearings, or the clutch release bearing?

What does everyone else think?

[glang]

Whats the noise like in 4th gear when the layshaft isnt under load? The release bearing if worn should only be noisy when its operating the clutch....

[Anthony]

No noises in fourth gear,

I'm guessing it's the layshaft bearings?

[glang]

Its almost impossible to distinguish between a layshaft and a mainshaft tip bearing problem as they both go quiet in 4th and both are known failure points for these gearboxes. Anyway it doesnt matter as both require a gearbox strip down to replace and both will undoubtedly need attention at about the same time.

The trick is to do this work before a major failure as that could result in damage to gears which are no longer manufactured....

One thing, have you checked the oil level? The oil capacity is only 1.5 pints and it seems to run out very easily😬 

[Nick Jones]

First gear will always be noisy on the 3 synchro boxes as it is straight cut. 

However, second should be much quieter and third better still so if if they are making a racket then layshaft or mainshaft spigot bearings are both suspects as already mentioned.

Nick

[Anthony]

Thanks Guys,

I was at the Triumph International show at Stratford at the weekend and all the other Heralds had completely silent gearboxes ...... mine sounded like a bus!

[Antonnick]

Just for info, my new exchange gearbox is very noisy in first gear, like Nick Jones says but all the other gears are quiet.

The reason I wanted a new one was because second and third were very noisy.