4 synchro box noisy in neutral

[Ronniebiggs]

Hi all,

My 3.4 Mk2 has developed a whiny noise when in neutral. The noise stops when the clutch pedal is depressed.

I'm suspecting the large bearings that support the mainshaft, but could it be the needle rollers on the constant pinion shaft? It looks like the transmission will need to come out after Goodwood but I'd appreciate anyone's experience of replacing these bearings - and how best to diagnose the likely culprits.

By the way, the 'box is full to level, and all other operations (including overdrive) are fine so I've hopefully eliminated lack of lubrication!

Cheers

Jay

[Tilleyjon]

Hi Jay
generally these symptoms would indicate input shaft bearings or layshaft bearings, the needle bearings are a common issue with these gearboxes.
If you are stripping the gearbox down, change all the bearings, check for wear or damage on the gears and shafts etc. but if all else is OK the gears/shafts should be OK, but while its out do all the bearings, it is enough work to get it all out so you may as well do the full lot.

The gearboxes are fairly straight forward, just have a good clean area to work and be systematic in your approach, then it will all go back together with no problems.

I am about to strip a 3.4 all synchro box, I will take pictures and post them when I do.

Jon

[Tim.T]

seconded..the issue is most likely 1st motion bearing going bad.. seems to be a common issue with these boxes..