effect of thinner gearbox oil

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350matt
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effect of thinner gearbox oil

Post by 350matt »

So then gents


in the continuing sage of trying to squeeze every last erg from a rexi I've come across this extra thin gearbox oil from redline, which is a new addition to their line

https://www.redlineoil.com/mt-lv-70w75w
from here
https://www.redlineoil.com/gear-oil-for ... nsmissions



basically its a 70W/ 75 compared to the normal MTL of 75W80 which we know works well
both are GL4 which is required for good synchro life

but potentially the thinner oil will give less drag and potentially a quicker shift

thoughts ?

its available here in the UK and I'm considering swapping over to it as I'm on the normal MTL now and it made a good improvement for me when I did the swap about 20K miles ago
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Re: effect of thinner gearbox oil

Post by Conan »

Hi Matt,
I really wouldn't bother with the RX-8 box
The gearbox will only allow you to change so fast anyway without damaging it which is why I think people can have problems with the quickshift.
If you had straight cut gears it would be a different story
I used to grind 50% of my dogs off when racing for a quicker no clutch shift
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350matt
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Re: effect of thinner gearbox oil

Post by 350matt »

Well I was kind of thinking it was time to refresh the oil anyway so why not give this new stuff a go as its the same price as the regular MTL
more interested in the reduction in friction to be honest
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Re: effect of thinner gearbox oil

Post by warpc0il »

If there was any reduction of friction then the synchros wouldn't work.

If it's really GL-4 then it's the same friction.

There might be slightly less pumping losses, though that's difficult to prove in a gearbox, and I'd be worried about the film strength.

It would likely make the box even noisier in neutral.

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Re: effect of thinner gearbox oil

Post by 350matt »

I'm not quite getting the positive energy from you on this one Dave....

I've seen that some chaps have tried it on the US forum with good results hence I thought I'd ask the question prompt the debate
its considerably less viscous at 100 degC so its got to be worth some drag
just what does it do to the rest of the experience really

still nothing ventured nothing gained
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Re: effect of thinner gearbox oil

Post by warpc0il »

Given that it's GL-4, it's unlikely to do any harm.

It might make those initial cold changes smoother, as they're down to the cold oil being a bit too thick.

Try it and report back?
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Re: effect of thinner gearbox oil

Post by 350matt »

looks like some chaps have been using it a while
https://www.rx8club.com/series-i-tech-g ... id-270351/

I think I'll give it a go
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Re: effect of thinner gearbox oil

Post by 13Black »

This reminds me that something some of the MX-5 folk do is 50:50 standard Redline gearbox oil & their Lightweight Shockproof gear oil.
Not sure how well an 8 box would respond to it, but my own isn't exactly a joy to shift with anymore, so I've been considering giving it a go somewhat as a last hurrah.
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