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S2a Gearbox making bad noises.....


Betsy
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Following a long layup, I got the S2a started last week. As I normally do, I press the clutch in before cranking to reduce drag on the engine. Once she was running, I let the clutch out. When I did this last week, there was a 'thud' from under the car, but she kept running and whilst in neutral was fine.

When I went to drive her, I found that all gears except 4th were accompanied by a fairly loud whining/whirring noise. The noise went away if the clutch was depressed, but always there when under power. In top gear she was quiet as normal and drove well.

I dropped the oil when I got home and what came out was a horrible grey coloured yuk. There was a full quantity of oil in the box, and the transfer box, but it was obviously water contaminated.

New oil has failed to quieten it down, so am now resigned to pulling the box out and repairing.

Has anyone got an idea as to what has broken from my description?

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yeah, 4th is straight through on the mainshaft. You're often left with only 4th gear if the layshaft fails. It would do it good to have a full set of bearings anyway. I'd guess with the water in the box the bearing races have rusted and pitted, it may quiet down in time but up to you, personally i'd pull it and inspect.

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the layshaft bearings almost certainly... 4th gear is direct through drive. meaning while the layshaft does spin because of the constants, its not under load, and even a reasonably nasty bearing will quieten.

these boxes, luckily are childs play to strip. the only difficulty you might come across would be removing the rear layshaft bearing race. i was taught a method to make it literally fall out.

its almost certainly because of some degradation of the oil, or contaminants, possibly rust. if so, there could be rust on the gears which means the case hardening is comprimised... depending on how you use it, youll probably get away without replacing gears etc.. if its only a standard engined toy, not used very often and when it is, only used for light driving (i.e. not a tw**) itll be fine for years and years! but if you go hard on it, you might get away with that, but keep it in mind that it might break.

anyway, id just strip it, check it, replace the layshaft bearings and anything else you feel may need it, and put it back together..

the only fiddly bits are making sure to note which selector spring and balls go where, and putting back in the constant gear and spacer with the bellhousing at the same time (which depends on how youre going to strip the box). just find an overhaul manual or instructions (theres a thread on here) and go for it!

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Many thanks chaps. I have previously rebuilt this box, along with the transfer box and the engine about 30k miles ago.

Since then its been fantastic, and I am really kicking myself for letting this happen. I take the car green laning quite a bit, and the last trip was a very wet one. I should have changed the oils before parking her up.

I have put a few miles on her over the past few days, and it does seem to have quietened a bit. I might give it a few more before deciding if I want to remove and strip. I don't do many miles, and she is standard engine and running gear, so the box is not normally under stress.

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In my experience you will find that the bearings will be more prone to rust than the gears, my salisbury front axle when i got it had badly rust pitted bearings and the gears were just dirty and washed clean, it had neen left full of water. I put it down to the steel of the gears containing more chrome in the alloy makeup than the bearings had.

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