Hello,
Does anyone know roughly how much torque the 1.3 awd Terios gearbox can hold. It seems to be quite weak to me. Are there ways to beef them up?
I don’t know a real lot about these in particular. But this type of thing will be weak and there won’t be anything much you can do other than: running the best oil you can afford; and making sure the box does not get hot. I would not want to shock load it with huge torque.
they are very very weak. the gearset in them is super small. almost looks like they just used the set out of the gtvi. it is a common problem for the gearboxes to fail when driven normally
Yeah, I thought they are weak. Are there no ways to strengthen them? I bought the Terios and it had water and oil mix in the gearbox and the oil has never been changed. Then I changed the oil and the gearbox sometimes was crunchy. But I did survive at least 15 aggressive launches on a stock k3ve2 engine.
At the moment the Terios is off the road as it has major rust issues and a cracked piston. So when I will be working on it, it may get a gearbox swap.
I’m having problems with finding a suitable replacement gearbox that will allow me to keep it AWD. So I might try to strengthen the gearbox.
What are the weak points in the original gearbox? Is it certain gears or the shafts?
Also does anyone know how good is the 1.5 Terios gearbox?
The reason why I am looking to upgrade it is I bought a K3vet and unfortunately the 1st cylinder was rusted. So I decided to get new oversize pistons Hwaskie pistons. As I have everything apart I decided to also get fake Carrillo Forged I beam rods and a TRD 1.5 mm head gasket to reduce compression.
So in the future I will have that engine in, and need to sort out the drivetrain. Also I’m doing major rust repairs on the Terios, so I have everything apart. So it’s the best time for me to upgrade the gearbox now.
why lower the compression more?? they are already 8.5:1 
stock gasket it steel so that won’t fail… I’d even be suggesting that, if you have ethanol available at the pump, to increase compression! 10 or 10.5:1 would be ideal for E85 and 1.5bar boost no probs 
that’s my $0.02 anyway
as to gearbox, you’ll struggle to find anything strong that’s made by Daihatsu, sadly! unless perhaps you can get a set of gears from one of the light trucks to fit…
One of the bores was badly damaged by rust. So I had to put oversized pistons in. I went with Hwaksei cast pistons. They are much cheaper than Daihatsu pistons and are strong enough for my build. They are also ceramic coated. But they have a much smaller dome than the stock pistons. So with the thick gasket I will bring the compression back down to 8.5 8.8. Also I have had my head already skimmed once and will require my block to be skimmed.
Also unfortunately in England there is hardly any e85 and there are no places around me for sure. So high octane fuel is a problem.
And what light trucks?
Thanks 
what… or who on earth is “Hwaksei” ?! they look like a Japanese manufacturer and a close copy of the K3 turbo pistons, from a quick google search. never heard of them though… if they are in fact Japanese then it’s possible… maybe… that they took over Daihatsu production from Sakura piston co. after they closed down? stick 'em in and see!
Yeah I couldn’t find anything about them. But I’ve been told they are Japanese. I am still waiting for the parts to come in.
bump
What was the outcome? Did the Terios gearbox survive? Looking at doing exactly the same.
Unfortunately my terios had major rust issues and other problems. So I’ve been sorting other things out. Also I will be running the engine in N/A for some time and then I will turbo it. But as soon as I will have some results I will post about it.
My stock Terios gearbox has had a lot of abuse, and unfortunately recently it broke. It was difficult to get into 1st and second gears, and the shift fork for these gears broke. I managed to find a new genuine replacement gearbox to put in. With the old gearbox out, I will take it apart to see how the components look and the potential improvements that can be made.
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Been quite some time. But it’s been 4 months since I’ve boosted my Terios. The replacement gearbox is holding up very well. Also I took my old gearbox apart that broke and it was the easiest fix ever. A pin that goes though the aluminium shift fork and the steel shaft for 1st and 2nd gear has worked its way loose and therefore I was locked out of gears.
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The gearbox is very compact by the gears are surprisingly solid, with the exception of 3rd gear that looks quite small comers to others.
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Currently my Terios is on 20psi of boost in a 16G TD05R and the engine, gearbox and diffs are holding up very well. I am using redline MT90 oil in the gearbox which helps, but it’s very expensive. The clutch however is not holding up. But I will have something sorted out for it.
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Hopefully the gearbox holds up with a new clutch. Would be a shame if the failing clutch is the only thing keeping the gearbox alive…
And 20psi… hoohaa sounds like a weapon 
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Made a diy clutch upgrade by using 2 diaphragm springs instead of one and still use the original disk.
The gearbox held up well for roughly 6 weeks of abuse including a drag racing and lots of pulls in the street. But 3rd gear finally gave up and disintegrated. But it is the smallest gear compared to the others, so was kinda expected to happen. Gear 1 however holds up perfectly with ~12 psi 2 Launches.
So, the Terios gearbox is not as weak as others are claiming. It will last forever with the stock k3vet swaps and probably up to 200 up at the crank. Not sure how much power I am making, but will find out in the next few months.