Rattly noise that started today

[davidmorr]

I am after some help in diagnosing a problem with my 1850 Dolomite manual. I have been driving it around for a few weeks. It has some gear/diff noise but then is is 45 years old.

Today, something started clunking underneath. When I got home, I drove it up onto wheel ramps and had a look underneath. I was expecting that the exhaust may have become loose, or something else would have been apparent. But everything looked quite secure.

Then I went for a short drive to try to identify the clunking again. Oddly, it had stopped.

But there seemed to be something else going on. A rhythmic grinding/rattling sort of noise while in gear, particularly second and third, and to some extent first. In top it was hardly noticeable. It was less noticeable while the clutch pedal was in.

I made some recordings on my phone although the quality is poor. (You do not need a Dropbox account. Just dismiss the dialog and it will allow you to play the recording.)

https://www.dropbox.com/s/nedhgd64ofxzh ... p.m4a?dl=0
It can be heard as a rattly sound in the first half of this.

https://www.dropbox.com/s/50q4pxhvsoyk8 ... p.m4a?dl=0
I was a bit more organised. The rattly sound can be heard clearly after I changed into second gear.

I would be grateful for any suggestions as to what is going on.

Clutch? Engine/gearbox mounts? Prop shaft?

Thanks

David

[Carledo]

A noise that affects the car in the indirect gears, but not 4th (which is direct) is almost certainly down to problems with the layshaft/layshaft bearings/laygear cluster area of the gearbox. Don't want to be a prophet of doom, but that's what it sounds like.

Steve

[davidmorr]

I did wonder. Just puzzled how it came on so suddenly. I would have thought it would get noisy gradually.

Ok, so what are the options? Is it repairable? Or would I be better to try to get an exchange gearbox?

It has a single rail gearbox.

Rimmers have some but do not ship them to Australia.

[xvivalve]

Were it a Sprint 'box, where the layshaft runs directly in the alloy casing, a replacement 'box would probably be the easiest/cheapest solution, but I believe in the 1850 gearbox the layshaft runs in needle bearings (though I'm happy to be corrected) so a repair might be a better option if the wear isn't too far gone...but remembering from the days of Jonners, he'd rebuilt gearboxes with new needle bearings only to find the manufacturer had gone metric and the closest equivalent were very slightly of smaller diameter which caused a premature and fairly rapid secondary fail.

I may have a used 'box from a '74/'75 car, but it's currently an unknown quantity though I have had the engine running so I could test it but not under load...it wouldn't be the first gearbox I've sent overseas, but I've no idea what it would cost...

[davidmorr]

Yes, that is the problem with repair, isn't it. You have to remove the gearbox and dismantle it to find that it is too damaged to repair.

As for shipping a gearbox to Australia, yes, I can imagine it would be expensive. It is a trade-off between how fast you want it vs the cost of shipping. Apparently sea mail at present really is sea mail, and takes around 7 weeks to get to Australia. otoh, by courier, it cost me $50 recently to get a few small items, so a gearbox could be lots of money.

[Carledo]

I can't watch your dropbox videos cos I don't have an account. But from the written description of the sound effects and their variations i'm willing to make a guess, which is that you have chipped a tooth on the laygear cluster probably the gear that is driven by the input shaft, at the very front.

The layshaft on the 1850 box is also fixed in the gearbox case (as on Sprint) the laygear is supported on the shaft by needle rollers and end float is controlled by a pair of thrust washers. It's pretty much a universal constant in gearbox design for RWD. A 3rd shorter shaft carries the reverse idler gear.

There is another common fault on this (Herald derived) gearbox which is failure of the mainshaft circlip This innocuous clip, all 10p worth of it, holds the 3rd/4th synchro hub and 3rd gear onto the mainshaft and can cause all manner of noises, rattles and difficult gear selection when it fails. But that's the clue to why I don't think it's this fault this time, you haven't recorded any difficulty getting the gears. In the worst case this circlip failure can result in the car getting irretrievably stuck in 1 gear (usually 1st or 2nd) but ALWAYS makes selection harder at least.

The gearbox has always been notorious for its weak layshaft and bearings, not many are quiet in the indirect gears, so perfection isn't really an option! The weakness is largely in the case hardening of the surfaces the carrier needle rollers run on both within the laygear cluster and on the layshaft itself. I'd say of all thse boxes i've dismantled over the years, only 20% max have had layshafts and laygear clusters that can be re-used safely and I ALWAYS replace all the needles as a matter of course. Just how bad yours was before the failure I couldn't say. But every little extra bit of play makes a catastrophic failure more likely, when it actually happens is in the lap of the gods!

Steve

[xvivalve]

You don't need an account to listen to the files, just dismiss the first pop up window that appears

[Gerard]

There is a Dolomite gearbox on gumtree for $40.

https://www.gumtree.com.au/s-ad/miners- ... 1293480824

Cheers
Gerard

[cleverusername]

I am a little bit confused by the description of the layshaft running directing in the casting? Surely it must sit inside a bearing and therefore the shaft doesn't directly touch the casting?

Meaning that you should be all the replace the bearing? It seems a very odd design otherwise.

[Mad Mart]

The shaft does not "run" directly in the casting, it is held there with a fixing plate (129938) which holds the reversing shaft also. The gear assembly actually rotates on needle bearings.

[xvivalve]

The casing IS the bearing...similar to the clutch cross shaft in your Sprint...

[cleverusername]

The casing IS the bearing...similar to the clutch cross shaft in your Sprint...

So if I am understanding correctly, there is no way to replace a worn layshaft baring once it is worn?

That seems like a crazy design.

[xvivalve]

After my TR6 had done over 150,000 miles the lay shaft started to chatter and due to damage done the remedy was a replacement casing. I suspect it had far exceeded its anticipated design life!

Unfortunately the debris also found it’s way into the overdrive and wiped that out too.

These were ‘A’ type components and even 25 years ago the bill made me wince!

[Mad Mart]

The casing IS the bearing...similar to the clutch cross shaft in your Sprint...

So if I am understanding correctly, there is no way to replace a worn layshaft baring once it is worn?

That seems like a crazy design.

Please see my reply above Alun's. The casing is not the bearing!

[cleverusername]

The casing IS the bearing...similar to the clutch cross shaft in your Sprint...

So if I am understanding correctly, there is no way to replace a worn layshaft baring once it is worn?

That seems like a crazy design.

Please see my reply above Alun's. The casing is not the bearing!

That isn't what xvivalve is saying. Are people talking about two different things here?