Meadows gearbox repair

[PaulRM]

I have begun stripping, faultfinding and rebuilding the Meadows box on my PA Javelin. I have the very useful, extensive additional notes provided thorough the club technical resources. However neither these notes, or the workshop manual, mention effective and non-deleterious removal of the large lock nuts holding both main shaft and primary shaft bearings in place, necessary of course before pulling of the bearings. (The shafts then being able to be removed from inside the box). My lock nuts are on VERY tight. I've tried locking either shaft in a vice and turning the nuts: no go. One has here to be careful not to damage splines or gear teeth. Have other members 'locked' the box (after removing side cover and selectors etc) by engaging fourth gear and second gear in order to lock the rotation of the shafts? Have they used heat on the nuts? Or have they split the nuts and used new ones? Any advice appreciated.

[PaulRM]

Being a bit pressed to disassemble the Meadows box as I am due to visit Southern section spares for some bits before lock down in 3 days time, I tried engaging fourth and second gear at the same time, effectively locking up the box. I then secured the shafts at both ends of the box to stop them starting to work their way out out of the case when force was applied to the nuts. I secured the box properly and used a stilton and extension to remove the nuts. Slow but firm increase in pressure loosened them. I shall continue to document bits of the renovation if members are interested. From the condition of the bearings this box looks to have been recently partly restored. However the case is worn and will be replaced. Also the layshaft is very worn. Before disassembly by the way, gear changing when driving was was fine, but the gearbox rattled a lot under load. This on a 'restored' car I bought two years ago.

[Keith Clements]

They need to be tight and glad you sorted it. Although having rebuilt dozens of boxes I do not remember how I did it. I have an adjustable spanner which fits. Stilsons are not recommended. I doubt if spare nuts are available.
I think i held the shafts in a vice with plastic jaws.
Great if you can document with pictures.

[PaulRM]

After stripping my gearbox I headed down to the Southern section spares department (aka member Ian Roxburgh's parts store and workshop) to evaluate wear in the box with someone who has had experience rebuilding this particular gearbox. The conclusion was that the box had been carefully rebuilt fairly recently - probably within 10000 miles- with minimal wear to the bearings. Spectacular wear however was observed on the replacement layshaft. See pictures attached. This is definitely not an original Jowett shaft. It was bright - relatively newly machined - and had only, visibly, ever received the aftermarket 'fullwidth' caged roller bearings on its surfaces. I'm including pictures of the shaft. Ian said this was the worst he had ever seen. Bear in mind mine was a gearbox from a recent restoration car that worked perfectly apart from an ever increasing rattle under load. It makes no sense that the previous gearbox rebuilder would have knowingly fitted a duff component, given the rest of the work done including rebushing the case.

My conclusion here is that the shaft had not been sufficiently hardened during manufacture. It marks with a file easily - which it shouldn't. I did some home work on this and discovered that a while back that a company in England had been commissioned to supply Moss Brothers with newly manufactured layshafts for the MGA. Several MGA owners reported severe wear after very low mileages after installing such shafts. Moss did a hardness test on some of their stock and found it to be way below par. They came out at RC50 - way below the required RC 60 of such a component. Here is an excerpt from their report:

"So there is "hard", and there is "bearing hard". RC 24 is definitely soft, not hardened.
RC 49 is hardened, but not as hard as would be desired (or required). A quick search of
bearing suppliers yields a consensus that a shaft to be used as inner race for a roller
bearing should be RC 60 minimum surface hardness. While the Rockwell "C" scale for
hardness is roughly linear, wear resistance is not linear. A relatively small change of
hardness results in a relatively large change in wear characteristics. 50% increase in
hardness can yield 50X increase in shaft life. Roughly speaking, the difference
between RC 49 and RC 60 could yield 20X increase in wear resistance. When you
invert the fraction, the difference between RC 60 and RC 49 could yield a 95%
reduction of wear life (roughly speaking). Therefore, as a roller bearing shaft is
concerned, RC 49 may be "hardened" but is not hard enough. When the shaft can be
scratched with a file or hacksaw blade, it is not RC 60 hardness."


All layshafts in the Jowett or Meadows boxes show wear - more on one side than another. However these pictures tell all. My concern is whether the shafts supplied to JCS are all insufficiently hardened or whether mine was a 'one' off. Of course I have no conclusive proof it was sourced from JCS, but then where else would it have come from?

Have any other members had issues with this component after rebuild?

[Keith Clements]

Thanks for the detailed comment.
Are you sure the layshafts were supplied by JCS and not by another supplier or made by the rebuilder themselves?
Your comment about Moss is echoed on many other parts produced by them and by other parts suppliers. It is a combination of poor specification by the requestor, poor engineering and cost cutting by the manufacturer, and poor quality control by the retailer (and by the purchaser).
To ensure this does not happen requires an immense amount of knowledge , experience , time and tooling . Very few Jowett owners are prepared to pay for such a service, even if it is available.
This forum tries to redress the balance and make people aware and share their experience and knowledge.
Thank you.

[PaulRM]

Hi Keith. Yes, I'm not sure the layshaft was supplied by JCS, and by the way I'm not implying any deficiency in the actual parts service offered by the club. I'll be ordering another shaft from JCS if available.

[Forumadmin]

I have seen more badly worn layshafts than that on what were probably original boxes, some down to 3 mm of wear. I have no idea on the history of those boxes. Jowett boxes usually require regular topping up with oil which I am sure is the usual cause of premature wear. Checking the oil at every other petrol fill up is not something people usually do.

[StevenGray]

That failure looks like a repair has in the past been done by cold metal spraying which has subsequently failed.

I have certainly seen similar failures to that on shafts that I used to get reclaimed for crushing equipment where the loads were significantly higer than in a vehicle gearbox

[David Kemp]

This is a bit late as you have your box apart , however for others working on their gearboxes , hold the shaft with an old clutch plate on the input splines, I even ground some flats so my vice could hold it easily.
It helps to have swivel vice so you can support the other end of the box on your work bench.