noise from where

[horrace]

it may be nothing to do with it, but ever since i had a new gearbox fitted i am getting a high pitched wooooooooooooooo noise (bit like an owl with only a twooooo no twit can be heard). the noise is most apparent when doing 40-50mph. if i drop the clutch the noise stops immediately, it may be that the noise is there through all the gears but due to higher revs going through the gears it cant be heard? any clues here?

[bmcecosse]

Bit obvious I'm afraid - but plenty oil in the 'box?

[horrace]

yes checked that and dropped the diff oil out and replaced it. could it still be gearbox or diff if it only is heard when the engine is driving, not free wheeling?

[les]

How new is the new gearbox? I'm thinking if the noise wasn't there before the box was fitted, it would be the gearbox to blame,or more accurately the bloke who built it!

[horrace]

hi les
gearbox was a mixture of 3 i gave to a gearbox rebuilder, which he stuck together to form one good gearbox. why do i only get noise when the engine is driving not freewheeling?

[les]

Possibly a case of mixing gears, gears tend to wear into each other and if they are seperated and mixed with others they can often whine.

[bmcecosse]

Ah - so he has used a mix of gears that have already 'run in' against other gears. Not surprising then that they are a bit noisy! Hopefully it will improve with running. You could try some STP in the box - although it may affect the syncromesh operation.

[horrace]

ok so we are convinced its the gearbox, not diff or anything else then?
i "like" your theory on run in gears, sounds like a good answer.
He always rebuilds with oldstuff as he reckons the new made gears are cack.
The Gearbox dude suggested i run it on a 70/80 gauge gearbox oil not the normal 20 50 engine, maybe ill give that a whizz and see?

[les]

Well convinced it's the box is only because that's when you say the noise started, it would not be impossible, but highly unlikely
for another incident to be the cause of the noise the moment you fitted the gearbox! The suggestion to use heavier oil could be because your rebuilder knew of the possible consequence of mixing gears but to be fair we don't know for sure if he did.

[horrace]

yes thats what i think, but you know stranger things have happened! no reason why i shouldnt try the different oil?

[les]

Well I'm no expert but try it, might be a bit more drag and not sure if the syncro will suffer if it does then refill with sae 30 and perhaps check out the suitability of some of these additives that may quieten it down. Of course something not mentioned yet is bearings, your man would hopefully have used new but if not that may be another possibility. Again it all seems gearbox related.

[lambrettalad]

was only the box changed? did you change the clutch etc ?

[horrace]

no didnt do clutch that was done 2000 miles ago

[lambrettalad]

does the noise change with different gears selected? e.g. at the top of that gears rev range?,on a curve?,on the overrun?

[horrace]

Its most noticeable at 40-50mph and pretty much disappears at 60. Not really audible in other gears but this could be due to engine noise.doesnt do it on over run

[lambrettalad]

my best guess then would be early signs of bearings,i had a similar problem with a GT6,which turned in to a rattle as time wore on

new set of bearings cured the noise

good luck

[les]

I'd be surprised if the guy didn't replace, at least the bearings. Or would I! Why not have a chat with this man and ask what he did?

[horrace]

i gave him a box of bits and asked him to make a good box out of it, he did say that 4th was not from the same box so that kind of figures. he didnt replace the bearings as they were ok

[lambrettalad]