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Building a stronger series gearbox can it be done ??


Aussie80inch

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Would that require milling the casting to take the bigger bearing?

What other improvements can be done? Oil cooler? There have been huge improvements in lubricants over the last few decades, I wonder, considering the bronze, what could be done with newer oils?

And could we seal the damn selector shafts?

G.

It would require milling a new bearing seat, which would have to be professionally done using CNC mill as it's quite important that it is right haha

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What other improvements can be done? Oil cooler?

 

There's no oil-pump.

But that doesn't stop you using a small electric [Holley rotary-vane type] fuel pump to circulate the oil through a remote-mounted cooler. That's what we did a few decades ago on the Escort rally-cars where we had Salisbury limited-slip diffs handling 300BHP and the drivers were cooking them on twisty forest stages.

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Sure, yes, But is lubrication a problem? Perhaps those who use series in the warmer climes, like France, Australia and other far off places, could chime in with experience? DO series boxes cook their oil?

Or is there a particular bearing that could do with extra oil, and have an electric pump with an outlet directed on to the bearing/gear?

I don't think the series box needs lube help, but in the spirit of the thread I'm provoking the questions.

Mike,

CNC machining that casing shouldn't be a problem, lots of good reference points nearby. I must dig out a casing and see how strong it is in the area, so as to see how much metal there is there.

G.

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An extra cog is pushing it, not without machining a new lays haft and modifying the main shaft gear set to allow for an extra gear. I have a casing about somewhere too I think so I'll check that for meatyness too

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I dont think heat is that much of a factor in the series box, going from australian use, its been trying to put too much torque thru them that has failed any i have had. One a four litre petrol six, and the other a 3.8 ltr diesel 4 . In two cases this has resulted in snapping the lay shaft. Full synthetic oil would help protect bearings , but that wont help the bending of the shafts when two gears are trying to force them apart . Third and top seem to be ok for a heavy right foot, but nothing below. JMHO

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The only time I broke a box was when a series 1 military box broke it's layshaft, right on the step. The earlier layshafts had the gears as separate assemblies to the shaft. The military layshaf was beefier, but all the stress accumulated at the abrupt change in diameter.

The series 1 still got me home, broken shaft and all.

So, the flexing of the two shafts is a concern. What can be done to address this?

Obvious, though useless, ideas include: thicker shafts, shafts made from better stuff, and better support for the shafts.

Can the layshaft be supported by a slipper pad? Like is done to diffs sometimes? They call it "pegging", I believe?

Or does the casing need external bracing?

G.

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I personally believe it all stems from a rubbish rear layshaft bearing which then allows the mesh to become sloppy.

If you have ever pulled through say third gear from a low chunter to accelerating you go through what can only be described as the natural frequency of the bearing. I.e. It messing it's pants. This is all because of the poor quality cage and the lack of size in comparison to the rest of them.

I don't believe that flex is much of an issue with the later machined one piece layshafts however the "seats" for the constant mesh gears can shear due to the lateral force applied by the helical cut gears. Once these have sheared the box will still fun and feel fine so long as the pieces don't make their way between two gears. I would imagine this causes end float in the layshaft, however mine is like that at the moment and has been running fine since I found out about it with no noises or excessive backlash.

It would be possible to remedy this by welding the constant gear to the layshaft in position before the seats break, however I fear this may cause a weakness due to the heat affected zone.

Ej I don't mean to say it must be CNC machined, a decent machinist would be just as good, in fact for a one off, probably quicker to be fair.

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