Hi all wondering if you could help me with my gearbox swap on a century 100. Need to rebuild box and have ordered parts from John (SOS) but got a bit impatient the other day and put the gearbox from my SJP on it for its maiden run on the tinny. Any way, the SJP gearbox is nice and tight and does not seem to have any issues. Took it out and noticed a whining noise coming from the gull. Gearbox had just had an oil change with 85 - 140 multigrade so it had plenty in it. Came straight home sourced some 140 EP trans oil and also some Lucas additive to thicken it up a little bit. Dumped multigrade and added EP and additive tank tested and still have a whining noise but nowhere near as loud, but it is still there. Have I just made a bad call by putting the SJP gearbox on for some reason it isn't a suitable match and I am unaware of this or are there other gremlins at hand here? Your advice would be appreciated.
Cheers Bob
100 Century gearbox swap
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Still trying
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Collector Inspector
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Re: 100 Century gearbox swap
John has what are known as shim sets.
You need to shim the lash for the gears.
Let us assume that your gear set is nice............backlash and shimming is required or noise.
Simple as that.
BnC
You need to shim the lash for the gears.
Let us assume that your gear set is nice............backlash and shimming is required or noise.
Simple as that.
BnC
A chicken is one egg's way of becoming others
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Collector Inspector
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Re: 100 Century gearbox swap
And by the way....forgot.
The gasket end cap has to be the correct thickness.......once again John hasem.
BnC
The gasket end cap has to be the correct thickness.......once again John hasem.
BnC
A chicken is one egg's way of becoming others
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headdownarseup
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Re: 100 Century gearbox swap
Yep, as Bruce has mentioned it will be a clearence issue between the gears.
Too slack (worn shims, sometimes there's 2 of them, 1 thin and 1 thick) and the noise will increase (despite having fresh oil), too tight and there will be a whole lot of other issues besides noise.
I'd always try and stick with 140 grade oil for the older designed gearboxes. Buying in bulk quantities seems to work out cheaper overall than 1 litre bottles all the time.
They're quite simple things really once you get your head around them.
Just about all of the older type NON SEALED 40/100 direct drive gearboxes will fit onto a century motor with no problems, so using an SJP gearbox shouldn't have any bad repercussions. You dont say whether your original gearbox is a clutched or direct drive box?
When your original gearbox is back together again, grab hold of the prop shaft and see if there's any in/out movement. There will be some, but hopefully not too much. As a very rough "by the eye measurement" you're looking for about 3mm or so. See what it's like when it's together again.
Jon
Too slack (worn shims, sometimes there's 2 of them, 1 thin and 1 thick) and the noise will increase (despite having fresh oil), too tight and there will be a whole lot of other issues besides noise.
I'd always try and stick with 140 grade oil for the older designed gearboxes. Buying in bulk quantities seems to work out cheaper overall than 1 litre bottles all the time.
They're quite simple things really once you get your head around them.
Just about all of the older type NON SEALED 40/100 direct drive gearboxes will fit onto a century motor with no problems, so using an SJP gearbox shouldn't have any bad repercussions. You dont say whether your original gearbox is a clutched or direct drive box?
When your original gearbox is back together again, grab hold of the prop shaft and see if there's any in/out movement. There will be some, but hopefully not too much. As a very rough "by the eye measurement" you're looking for about 3mm or so. See what it's like when it's together again.
Jon
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Still trying
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Re: 100 Century gearbox swap
Hi and thanks for the replies. looked at the direct drive gearbox I'm waiting for parts to rebuild and saw the thrust washer behind the crown wheel and measured its thickness which was 2.14 mm and thought oh well I'll take the end cap off the SJP gearbox and see what the difference is, BIG DIFERENCE, THERE WASN'T ONE THERE? 
Well I put the washer from the dismantled box in there and put it back together and 
runs as quiet as a mouse. Shaft movement forwards and backwards is now 2mm. I did order new thrust washers from John with the parts I need to fix the other direct drive box I removed the washer from so that's all worked out well then.
Cheers and thanks again for your advice.
Bob
Well I put the washer from the dismantled box in there and put it back together and runs as quiet as a mouse. Shaft movement forwards and backwards is now 2mm. I did order new thrust washers from John with the parts I need to fix the other direct drive box I removed the washer from so that's all worked out well then.Cheers and thanks again for your advice.
Bob
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Re: 100 Century gearbox swap
Good to hear Bob.
May I just say........We All Like Pics?
Have fun
BnC
May I just say........We All Like Pics?
Have fun
BnC
A chicken is one egg's way of becoming others