What’s making my gearbox whine? …reprise

[Malcolm]

Thanks for all the answers to my recent post about my whining gearbox. You were all absolutely right -- the whining noise when driving in first, second and third gears is indeed related to the gearbox rather than the engine.

I was all excited about topping up the oil in the gearbox and having the noise disappear, but when I went to do so I discovered that the oil level was filled right to the top. Can't be the oil.

Back to square one.

Any other thoughts about what the problem might be?

[bmcecosse]

Yes - wear in the layshaft bearings. In 1 2 and 3 gears the drive goes through the layshaft - in # 4 it goes straight through - hence no whine. Start looking for another gearbox ! Often on ebay - Sprite/Midget one will do.
Of course - with light use it may run for many a mile yet - so don't panic!

[Cam]

I would not have thought that a whine was bad bearings (or bushes). More likely worn gear teeth in which case it's not a failure problem.

1st, 2nd and 3rd all use the layshaft as BMC says and if these gear teeth are worn then they will whine. 4th does not use these gear teeth so no noise. I personally would expect it to be ok, just noisy.

[Malcolm]

The current gearbox was bought - reconditioned - a year ago from a reputable Morris supply place, but has made the noise since the start, I think. Does this mean I was sold a lemon?

[aupickup]

phone the morris minor place where you got it from and see what they have to say

[bmcecosse]

If the layshaft and/or bearings are worn - the gears will be running slightly out of mesh - hence possible source of whine. Of course - it could be the gears WERE running out of mesh and developed a wear pattern - and then at reconditioning they were brought back into mesh and so now they whine !! Incidentally - there is nothing quite so wonderful as the whine from a set of straight cut close ratio gears - they also only whine in 1st ( all boxes are straight cut on first) and 2 and 3 gears with virtually none in 4th. So - maybe you have a set of straight cuts in there!! If so - lucky fella !! If it all really bothers you - you can take the side cover off and have a look inside. If it was mine - i would change the oil to 20W50 (because there is no knowing what's in there now) - and as long as it doesn't jump out I would keep on using it. Meantime keeping an eye open for a good spare box for stock 'just in case'.

[Cam]

If the layshaft and/or bearings are worn - the gears will be running slightly out of mesh - hence possible source of whine. Of course - it could be the gears WERE running out of mesh and developed a wear pattern - and then at reconditioning they were brought back into mesh and so now they whine !!

Sounds like a likely explanation, especially as good gears are now difficult to get and if a gear is in reasonable condition it will get used in a recon gearbox.

I have also heard that some recon gearboxes whine initially and then quieten down the the gears 'bed' into each other (well into the layshaft gears).

Incidentally - there is nothing quite so wonderful as the whine from a set of straight cut close ratio gears

Oh that's certainly true! I had the wonderful experience over 10 years ago of a highly strung 1380 high compression Mini running on a straight cut box. The noise that car made was mouth watering!!

So - maybe you have a set of straight cuts in there!! If so - lucky fella !! If it all really bothers you - you can take the side cover off and have a look inside.

Unlikely in a Minor box I'd say.

If it was mine - i would change the oil to 20W50 (because there is no knowing what's in there now)

That's a MUST!

[bmcecosse]

Straight cut gears certainly were available for Minor/Spridget boxes - and very possibly still are. Quite expensive though. I had 2 straight cut boxes - one in my Autocross/Sprint Mini and one in my Rally Elf. The whine as it hammered down through Glencoe in the quiet of the early evening will stay with me for ever!

[Cam]

Straight cut gears certainly were available for Minor/Spridget boxes - and very possibly still are.

Oh yes, just nowhere near as common as for the Mini boxes.

I had 2 straight cut boxes - one in my Autocross/Sprint Mini and one in my Rally Elf. The whine as it hammered down through Glencoe in the quiet of the early evening will stay with me for ever!

Ahhhhh...

[Onne]

Like the novice that I am, what is the advantage of straight cut boxes?

[bmcecosse]

Supposedly less power loss in the intermediate gears. Some say 'stronger' - but the fact is - the drive is still transmitted by the little dog teeth which remain exactly the same - the actual gear teeth rarely give any problems - unless the bearing start to wear and allow the shafts to move and the gears to come out of mesh. To be honest - i suspect they may have been less expensive to make - and so it was an easier/cheaper route for small volume manufacture to get close ratio gears.

[Onne]

all right. thanks for that, it's a bit clearer now