Gear Box

Hello guys,
I’m new here. I have Daihatsu Sirion 1.3 GTVi 2001 with K3VE2 engine.
I’m just wondering if there is a possibility to upgrade manual 5 speed gearbox to 6 speed gearbox? And if using electric turbo before air filter box would boost the initial torque?
I tried once with centrifugal high rev dc fan to push air before air filter box, i felt a bit of improved torque while start driving with 1st gear and so on.
Unfortunately, the fan was blown due to my poor electric circuit set up :cry:. Couldn’t find similar one as that fan was pulled out of retired electronic equipment.
Sorry for plain English as I don’t have much professional equipment and or dyno test things, etc.
I’m just using regular man tools in my garage workshop.
Thanks heaps in advance for any of your knowledge sharing


The long-legged 5-speed gearbox was always Daihatsu’s shortcoming.
Some here have suggested replacing it with a Toyota gearbox. Of course, if a six-speed would be available. This conversion would call for welding together both original driveshafts to those of the Toyota

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The gear ratios can be changed, but at significant cost - Google ‘Compact Motorsports’ who offer a revised set of ratios but the parts alone will cost you $5,000 NZD or £2,700 GBP before shipping. Then you can count on probably £1500 of work to have the engine & gearbox removed, ratios replaced, clutch replaced (since you’re in there already it’d be foolish not to), various other jobs that are worth doing with the engine out and then have it all put back in by a garage. It’d be cheaper if you can do the engine extraction etc yourself, and give a specialist the gearbox and new cogs to swap in, but can’t imagine you’d get much change from £4-500 for the job to be done by a professional. I’d say its probably a bit above the average home mechanic to split a gearbox and replace the innards reliably. Certainly I wouldn’t attempt it.

So yes, it is possible and I think some people on here have done exactly that, but you need deep pockets!

Re the DC fan, I’d not bother - all the guff about ‘electric turbos’ is just rubbish, it will take much more power to run than it will generate in additional air into the engine/power out. The reason that conventional turbos use exhaust gasses to spin the intake fan is that exhaust is basically a waste product which has no use, if you can harness this to increase intake pressure then its ‘free power’ - if you’re having to power the turbo with the battery, you’ll increase load on the charging system, which needs to be powered by the alternator, robbing engine power from delivering power to the wheels.

It will have a net negative effect.

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Please make an intro thread in this section to get you started in our forums.


You could fit a Sadev. Things like this are possible. How deep are your pockets? Same goes with electric super/turbo chargers. Garret or similar are about it. Anything else is like pissing into the wind. Award-Winning E-Turbo Technology - Garrett Motion

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[quote=“Granger, post:3, topic:5789”]…I’d say its probably a bit above the average home mechanic to split a gearbox and replace the innards reliably…[/quote]I had to do this, as part of my job. It isn’t impossible to do. One only has to be attentive and orderly. When in doubt, have an experienced person assist or supervise.
Over here, we have these self-help garages where one could either bring the entire vehicle or a certain component, be it an engine, gearbox or alternator. These garages always have an experienced and certified machanic present. It will only cost an hourly fee.
Principally, gearboxes function patently identical to one another. Therefore, splitting the gearbox from a Honda or Mitsubishi shouldn’t relavently differ from splitting that of a Daihatsu. Chances are, all three of these gearboxes could have been manufactured by only one manufacturere of which isn’t uncommon in the automotive industry.
How-to videos should also be in abundance.
Your biggest worry should be the availability of gaskets


big question is what are you wanting to achieve


As inspiration, here’s a link to how somebody over here went about it: Getriebe M300 1KR-VE zerlegen -

I took the liberty of condensing the post to only what was necessary and to make sense of it:

[quote=]…my experiences with disassembling the M300 transmission, which is also installed in the L276 and in the Justy…

…Since the gearbox is so small, it doesn’t weigh much…

…the scrapyard had cleaned it with the high-pressure cleaner, soon after it was removed from the vehicle, i.e. blown water and dirt into the transmission. Also slight traces of rustappeared on the differential carrier bearings…

…Doesn’t seem to be difficult. Usual 5 gears, just 4 gears with an attached 5th gear. Only a bit more modern, with shifting on both shafts, 1st and 2nd gear are on the output shaft, 3rd-5th. gear on the clutch shaft.
As a special feature, the 4th gear has needle bearings. All other gears have bushings. I didn’t disassemble the 3rd and 4th gear shaft, because it didn’t seem was necessary to do so.
The gearbox doesn’t seem to be meant to be disassembled either, because all of the connections between the selector shaft and the selector forks are designed as hollow spring pins, not screwed. That means you have to drive them out, that is, hammer them through with a pin punch chisel. Not exactly pleasant, but works.
There are 3 normal hollow spring pins and one with a barrel spring fitted to its circumference and one that goes into the steel claw that actuates the shift fork 1st and 2nd gear.

Remove the tin cover, then the 5th gear is in front of you. Both transmission shafts are secured with nuts. Two gears must be engaged in order to turn the nuts. So engage either 3rd or 4th or 1st or 2nd gear. Drive out the hollow spring pin for 5th gear, engage 5th gear by moving the shift fork, gearbox locks. You can then remove the shift fork and sleeve for the 5th gear. But be careful. Otherwise, the sliding pieces will fly off to the side. If you are attentive, you can also completely remove the 5th gear synchronization including the shift fork, without mishap, as long as it doesn’t get stuck on the toothing of the shaft like mine did.
After removing the 5th gear, the bearing of the clutch shaft is free, the gearwheel of the 5th gear is stuck on the output shaft. It has to be removed, otherwisedisassembly won’t go any further.
This also sits very tightly on the shaft. Heating it up with a torch helps, then it comes off. Below you can see the bearing of the output shaft, which is secured with a circlip. Unfortunately, it’s even tighter on the shaft, so you can’t get it off the shaft with just light hammer blows. It’s not intended that way either, because the retaining ring can now be spread and then releases the bearing.

Opening the case:

This is positioned using two locating pins, and they are slightly stuck in the grate.
Unfortunately, heating doesn’t help much. On the shaft side you can pry the case with a screwdriver. But not on the differential side. An M6 bolt with a wing nut helps as a spreader. There are two bosses cast onto these halves of the gearbox, for this purpose.
You can now separate the halves a bit until the bearing is stuck at the top. Spread and slide the circlip, until it clears the groove in the bearing. The case halves now come apart. The difficulty of this procedure depends on the amount of rust on the fixing pins.
…Driving out the hollow spring pins of the shift forks is easier than unscrewing the shift fork block completely. And above all, for the assembly you have to drive them out anyway. I did it the other way around, first screwing and then driving…
If you have knocked out the pins, you can pull the selector shafts and take the transmission shafts with the shift forks out of the half of the housing.
And then completely disassemble the shafts for examining.
When disassembling the shaft, always be careful not to fly off the small sliding pieces for locking the shift sleeves. Otherwise it’s a nasty thing and you can’t reassemble the gearbox.

…The 2nd gear synchro ring was defective, I had already suspected it. It’s broken as you can see in the picture…

…if you overhaul your drive unit, you should open the gearbox, possibly replace the spring washers or bend some yourself and turn them by 120° so that the worn areas in the shift sleeve carrier are no longer used…


Just backwards compared to disassembly, sealing is done with silicone sealant, look for tightening torque specifications…[/quote]


You can install a lower final drive, which will shorten all the gears and improve acceleration.
It would be a bit simpler than an entire gearset change.
Be aware that lowering all gears means your cruising rpm at 80-100km/h will increase (along with fuel consumption). So not the best solution if you’re doing a lot of distance driving.