Noisy gearboxes

["Slack Alice" Simon]

The gearbox on Chris Blakey's car was newly rebuilt by a recognised expert, and was emitting a noisy whine from the start.

7500 miles later it was making the same noise.
You can hear it plainly on the video clips.

I wouldn't be happy with it, but it has got Chris to Tokyo.

[Tony Betts]

Hi dave,

Is it that the gearboxs are noisy when the car is stationary. By the sound of it that's what you are saying.

Or when the gears are in drive.

Many people mistake rear axle noise, for gearbox.

It does tend to travel through the car.

Or even PROPSHAFT.

Tony

[Chris KC]

In fairness to recognised A7 gearbox experts, they do tell you up front (or some of 'em do) to expect more noise with a CR conversion as they employ straight cut (as opposed to helical) gears, and these are inherently noisy. That said - and I don't own a CR box 'cos I'm still waiting after an excruciatingly long time for a recognised A7 gearbox expert to ship me my gears back - I'd be surprised if it made that much noise when not under load. Possibly there are people here who do have them and can confirm.

[Peter Naulls]

I had a 4 speed box converted to Nippy ratios many years ago, it was very noisy under load (I was told to expect this) but didn't exhibit any unusual noises in neutral.

Incidentally the gear whine under load did lessen with use but it was never as quiet as standard 4 speed boxes I've used. I was told it was because the mesh of the gears was less good than the Austin ones.

Peter.

[daveg]

Tony - both gearboxes are noisy in neutral so prop and rear axle are not turning. Enjoy your break in America and have a rest I suspect I will be pestering you for bits when you return.

As Ian W suggested I tried both gearboxes in different gears:-

Modified to close ratio box - This is in a car so I lifted the rear wheels and tried each gear.  1st, 2nd and 3rd the noise was still present but in 4th it disappeared!

Original close ratio box - this is out of the car on an engine running on a test frame. Again 1st, 2nd and 3rd had the original problem but in 4th the noise was reduced but still not good. I know that the 3rd motion shaft bearing on this box needs replacing and the lay-shaft end float is excessive and need sorting.

Am I right in thinking that in 4th gear the drive is direct and the 1st and 3rd motion shafts are rotating at the same speed and so the inter shaft bearing is not in play and maybe the problem?

I will order some new bearings for the original box and sort out the lay-shaft end float and see how it performs.

[Tony Betts]

Thanks dave,

Must admit, we are loving it as usual.

In fort smith tonight,and have 2,500 miles on the rental car.

We fell upon a flee market today, and found what we have been looking for for years.

A vintage coin operated set of shop scales in working order. It's taken 10 years to find them at a sensible price, rather than the usual $1,500 and these ended up being stoopidly cheap.

Although they are heavy enough to feel like we have two passengers.

With your gearbox problem, asking how long it has been since running them. I find with cheaper bearings on dynamos. They dry out and get noisy very quickly.

It could be the same with the gearboxs, I noticed on older gearboxes with old oil. They stay lubricated almost indefinite.

Didn't get to email you after beaulieu, so will chat when I return.

Tony.

[Ian Williams]

It is very strange that you have exactly the same noise from both boxes, that said I have not come across a box which has been converted to CR gears that is completely silent, but your Nippy box is original so???. Some of the CR conversion sets which have been through my hands have not been the most accurately cut and one set was sent back it was so bad. I almost every case I have had to regrind the bore of the 1st motion shaft, as supplied the bore seems to be tapered from the new gear being shrink on and sometimes very rough from spigot bearing wear. I did manage to quieten down one very noisy set by running the gears in on a lathe with very careful application of a fine grinding compound. Layshaft's and bearings can be horrendously worn, if this happens the gears drop further out of mesh than ideal so it is not just end float that you should be looking to address. I have corrected this with either a better layshaft or had the shaft reground and made new bearings. Hope this is of help and gives you a few ideas to investigate.

[Hedd_Jones]

There was a CR 4 speed box in the green tupperware special I had.

No idea who did it, but it was horrendously noisy in everything except top gear. I put this down to it having straight cut constant mesh gears. It was far noisier than a an Austin 3 speed in a saloon!.

[Ian Williams]

Yes Hedd straight cut racing gears in a 4 speed box are very noisy but we are discussing helically cut gears in Nippy an SA ratio boxes, they should be no noisier than a regular 4 speed box.

[daveg]

Ian - I am beginning to wonder if the the gearboxes have different problems:-

Close ratio conversion - I am confident that the roller bearings in this box are not to blame having been replaced twice and made no difference. The inter-shaft bearing has also been replaced twice but I did not check the first motion shaft for distortion. It seems the replacement close ratio gears have problems - I came across a thread from the old forum where someone else was having very similar problems:-

http://pub25.bravenet.com/forum/static/s...3&cmd=show

The noise disappears on this box when 4th gear is selected - what happens differently in the gearbox when 4th is selected compared to 1st, 2nd, 3rd and neutral?

Original Nippy box -  Although quieter in 4th this gearbox was still noisy. I know there is a problem with lay shaft end float and the 3rd motion shaft bearing on this box. I will sort out these problems and see what difference it makes.