C64 box killers - post in here

Topics relating to the Lotus Exige S2 (series 2)
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Yes I figured the oil would be good for way into the 100s. I think some of the C64 theories are that the casing can get so hot that the gears start disengaging by a fraction of a mm - just enough to move the shear forces to a weaker part of the cog. Sounds far-fetched to me but wtf do I know?!

I've heard casing temps of 120+ being recorded on track, so it would seem that I'm a fair way under that but my sessions are short, it was a cool day and I'm not running 'serious' torque through it so all mitigating circumstances.
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Interesting thread, which I have only just come across after #138 had its gearbox taken apart (to install a Quaife ATB diff), and then reinstalled without replacing anything else! :D No issues were reported though, so, fingers crossed, seems like there is still some life in the internals.

On another note, came across this thread about 'wobbly JUBU 3rd, 4th 2006 Exige CUP 240': https://www.lotustalk.com/threads/wobbl ... 40.475524/

"As is It is difficult to say if it is too loose, but typical transmission are not press fit like the Toyota."

So, it begs the question as to whether Toyota boxes are too tight for circuit or hard road use?

Any thoughts on this?
2010 Exige S RGB #138
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Lankan wrote: Mon Aug 31, 2020 8:00 pm

Any thoughts on this?
It's (yet another) theory I guess. I think it's fair to say that the C64 has no single weakness, everything discussed in this thread and elsewhere just contribute to the whole package being weak above 260bhp/170ftlbs sort of region (but not bullet proof below that either!).

- Temp
- 3rd/4th thickness/strength
- FD strength
- Input Shaft Strength
- Casing Strength
- Synchro weakness
- Driving style/aggression

etc, etc. If you address 3 of those 6 things (for example) then I imagine your chances of a failure start to come way down - so it's about picking your spending limit and choosing your compromises I guess.
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Interesting thread

I had the 260 upgrade around 8 years ago, shortly after dropped a pulley size to match the 211 (275hp?) then I think a year later dropped another pulley size (can’t remember the sizes off the top of my head) because I just thought what the hell if it goes it goes.

I’ve had no issues in all that time using the Millers CRX 75x90 NT motorsport gearbox oil which I change every year without fail

I did however once try the redline gearbox oil for a year, really didn’t like it. After a couple of months changing gear became more notchy then when I changed it out the oil was white/Mayo coloured due to excess heat. Thankfully since going back to miller’s I’ve had no trouble and the gear shift is smooth again.

Interesting most gearbox failures had the redline oil in at the time, maybe just a coincidence though
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My failure happened with the standard factory oil, always ran redline after that.
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