Lagondaforum

Subject: Re: G9 gearbox

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Well Bill. You are now on my shoulder! Gearbox is out and the internals look in very good order with no broken teeth or play apparent and no cracks in the casing. So I do not propose to take it all to pieces this time and will simply replace the oil seals. However, I have discovered a cracked silentbloc housing, which is now in two pieces, on the rear bearing housing. I propose to attempt a repair and have also asked LMB for the price of a new casting. Tin hat on! My question is whether I can remove the rear housing, without dismantling the internals. I do have the latest book but David is not too specific on partial repairs. It would be too much to ask that it might, having removed the speedo gubbins, just pull off with the bearing in situ. Any advice or comments gratefully received.

Subject: Re: G9 gearbox

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Hello Adam

I suggest you have a word with Alan Brown, He still has some G9 bits and as always is very helpful.

Colin

Subject: Re: G9 gearbox

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Thanks Colin, will do.

Subject: Re: G9 gearbox

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For the benefit of others : - Adam, I have spoke to you but you should be ok to get the rear housing out. However, mine was very difficult. It needed a bit of heat on the aluminium housing and gentle prising with a knife edge tapped into the gap.
If you can face it, go further and inspect the bush hidden between the input shaft and the output shaft. If this does not get much lubrication it will, I think then cause the 2 shafts to "wobble" leading to possible breakage of the helical teeth.

Subject: Re: G9 gearbox

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Morning Adam,

My advice would be to go all the way now you are this far.
At least as far as stripping the main and input shafts.
A crack in any of these castings can be welded, I have done many but they do need carefull preparation first as they are usually a bit oil soaked.

Good luck and feel free to phone and ask anything, I know these boxes very very well.

Best regards,
Julian

+32 489712608

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Subject: Re: G9 gearbox

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Thank you Julian, The rear casting is now off with no problems and I will take it to a TIG welder next week. Too much mass for my Mapp gas!
The front horns were moving nicely, but only because of the input shaft movement. I shall reapply myself to that end and carry on with the full job.

Subject: Re: G9 gearbox

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Great Adam,

As Bill has said, the input / main shaft Spiggot bearing is very important, it should be moving on both internal and external surfaces but should have minimal play. The club have them in stock I believe, T8 and G9 use the same bearing.

Regards,
Julian

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Subject: Re: G9 gearbox

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Very happy to report that the gearbox is all apart and appears to be in excellent condition. No broken teeth, bronze bush fitting well, no blockages in the oil hole feeds to this and no apparent bearing wear. I guess it was well restored before my tenure! On the instructions of the previous owner, I have always filled with gear oil, perhaps this has been helpful. On dismantling I noticed that only jointing compound, no gasket, was used on the bearing holder and front/rear casting faces. Red hematite was used, I would use Blue Hylomar unless there are any other suggestions?

Subject: Re: G9 gearbox

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Well done Adam !
I am sure Blue Hymolar is fine or a very good quality silicone ?
If you dont have a magnet in the drain plug now would be a good time to fit one ?

Subject: Re: G9 gearbox

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Regarding sealant, I quite like Wellseal and there is quite a good debate on the web at http://www.model-engineer.co.uk/forums/postings.asp?th=99081 I agree with the sentiments here.

I keep most types of sealants to hand, including the wonderful loctite pipe sealer but if in doubt, it's Wellseal for me. I like to wear thin surgical gloves when I use it and spread it around with thin plant label sticks which can be found in pound shops.

Thanks for your useful advice Julian.

Colin