Gearbox removed, shaft question (with pics)
Discussion
Today i removed the gearbox from the Chimaera to try and solve the grinding noise that has been diagnosed as the spigot bearing. All went well, and i have found out the clutch is in very fine condition, as is the flywheel which we suspect has been replaced recently. The spigot bearing does seem to be the problem, since it is bone dry and full of rust.
The problem we have is that rather than damage the bearing, it has worn away the main gearbox shaft, which needs to be repaired before we can change the spigot bearing and reassemble everything
So, to the wisdom of PH, how can we repair this? Can the metalwork be built up again then ground down (as we have done to a few shafts at work), or can you get repair sleeves and slightly undersized bearings to match, or does it need to be replaced?
I will give V8D a call tomorrow to talk to them about it and see what they think, since i will be getting some bits from them anyways, but i did'nt know if anyone had any other suggestions.
Here are some pics to show what we are dealing with. The internal diameter of the bearing is 15.00mm, the thickness of the unworn part of the shaft is 14.97mm, and the worn part is 14.46mm if this helps at all?
And some other random pics from the day:
The problem we have is that rather than damage the bearing, it has worn away the main gearbox shaft, which needs to be repaired before we can change the spigot bearing and reassemble everything
So, to the wisdom of PH, how can we repair this? Can the metalwork be built up again then ground down (as we have done to a few shafts at work), or can you get repair sleeves and slightly undersized bearings to match, or does it need to be replaced?
I will give V8D a call tomorrow to talk to them about it and see what they think, since i will be getting some bits from them anyways, but i did'nt know if anyone had any other suggestions.
Here are some pics to show what we are dealing with. The internal diameter of the bearing is 15.00mm, the thickness of the unworn part of the shaft is 14.97mm, and the worn part is 14.46mm if this helps at all?
And some other random pics from the day:
Edited by lewis_sharman on Tuesday 18th August 00:24
You've answered your own question really 
You coud have it welded up and remachined but you'd have to take the input shaft out of the box.
If you're going to go to those lengths, and bearing in mind that the heat of welding MIGHT weaken the shaft anyway, would it not be wiser to replace the input shaft?
Can't see a repair sleeve being feasible as the shaft is not that large to start with; by the time you shave a couple of mill off it to take a sleeve (which won't add anything structurally to the shaft) you'd be working with a pretty pathetic diameter of metal for what you're asking it to do.
IMHO, of course
You coud have it welded up and remachined but you'd have to take the input shaft out of the box.
If you're going to go to those lengths, and bearing in mind that the heat of welding MIGHT weaken the shaft anyway, would it not be wiser to replace the input shaft?
Can't see a repair sleeve being feasible as the shaft is not that large to start with; by the time you shave a couple of mill off it to take a sleeve (which won't add anything structurally to the shaft) you'd be working with a pretty pathetic diameter of metal for what you're asking it to do.
IMHO, of course
Depends how much the shaft is damaged.
Turning it down and getting a bespoke bearing made would work. The bearing is just to hold the shaft central it should not be taking any load and the shaft only turns in the bearing when the clutch is disengaged.
Having said that you will still have to take out the input shaft to get it machined. So it may be better for peace of mind just to replace it.
Turning it down and getting a bespoke bearing made would work. The bearing is just to hold the shaft central it should not be taking any load and the shaft only turns in the bearing when the clutch is disengaged.
Having said that you will still have to take out the input shaft to get it machined. So it may be better for peace of mind just to replace it.
I suspect that when the new clutch was fitted the spigot bush was replaced too, but as it was pressed into the crankshaft it compressed leaving the hole for the gearbox input shaft with less than the required clearance required (15mm).
I'd be inclined to replace the gearbox input shaft, should be available from The Gearbox Man http://www.gearboxman.co.uk. When you fit the new spigot bush use a 15mm reamer to open out the hole for the input shaft after fitting.
I suppose you could buy the new spigot bush and try it for fit on your old input shaft (suitably 'cleaned' around the damaged area).
I'd be inclined to replace the gearbox input shaft, should be available from The Gearbox Man http://www.gearboxman.co.uk. When you fit the new spigot bush use a 15mm reamer to open out the hole for the input shaft after fitting.
I suppose you could buy the new spigot bush and try it for fit on your old input shaft (suitably 'cleaned' around the damaged area).
Shafts can be repaired by plasma hard chrome deposition and regrinding to size. Lot of work though, remove the shaft machine to make it parallel, chrome rebuild then finish size by cylindrical grinding as the chrome is very hard, cheaper to fit a new shaft, or a custom bearing as suggested.
sk7ine man said:
Sorry slightly O/T but how hard/easy was it to remove your gearbox/clutch assembly on the driveway? Considering doing this when i do the clutch change on my Cerb...
Surprisingly easy actually, it was the first time i had done anything like this but it was less painful than getting the wishbones on and off! I will write up a little 'how to' with pics once i get some better ones 
ETA
Once it was high enough on the stand it only took about 3 hours to get the whole lot out
Edited by lewis_sharman on Tuesday 18th August 22:24
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