I will choose to overhaul simply because you don't know how the recon one was done. Overhaul meaning you still have the control on the quality of the gearbox but of course, find the one with good workmanship.

Repair or Recon should be similar

Another option is get gearbox from halfcut shop. If it is cheaper a lot can consider halfcut option, i also change my Kelisa gearbox few years back with halfcut unit, halfcut shop also can offer warranty nowadays.

What's the problem are you encountering with the transmission now? Mind telling more why you came to conclusion you MUST replace/overhaul it?

yes should have asked that first

1) use lubegard platinum or K&W /KW TransX high mileage ATF treatment
2) change another ATF, use back your car model oil, perodua ATF, or Aisin ATF
3) no need change/overhaul gearbox unless you encountering leaking or completely unable to change gear.

Well that makes me feel a whole lot better. I was thinking to do that. You know... I have been with my foreman for nearly 20 years, but mechanic is still human need to feed his family... as much as I want to trust him... I always think to ask sifus first. Then they might say something that makes complete sense like you. Thanks!

What ATF are AND were you using? meaning b4 the service what ATF did you use? In your car now what ATF are you using?

**added**    What's the mileage of your gearbox now? meaning how many kms have you driven over the 18yrs.

assuming 160k km, as in 160 000 kilometers, and 20 years, that's a very old car.

varnish/gunk etc will be clogging up the transmission valves and torque converter etc so the functions will be delayed or even completely jammed until the fluids/ATF and transmission is properly warmed up (because fluids thin up/become more smooth after heated up)

even if you change your ATF on time, you only change out a portion of old fluids as a lot of old ATF is still sitting in the torque converter and connecting valves and pumps etc.
so it is of no surprise with the mileage and age of your car, issues start to creep up.

last question: yes, most certainly!
that's why follow owner's manual, follow oil spec.
and when in doubt, using back the manufacturer's (brand of vehicle) own lubricants would be best as most, if not all of the brands will have their on branded lubricants according to their own cars.

Agree with Quazacolt. Try simple and cheap fix first. Can also try lucas transmisssion fix. Read. It up and watch youtube on it.

If you are ready to spend so much to change gearbox, givr these fix a try. But dont do both at the same time la

Edit: its best to ask what atf your SIL is using. Does this happen when you get the car or only after you change atf? I forgot to share. Im a first owner of my city. Once, i changed atf and atf filter just like you. And a couple months later i started having some issues with my gear box. I didn't think much about the oil change. And issue happen on off for a year. I change the atf again, without doing anything else and viola! Problem solved.

You can try that first too.

It is NOT about brand, it is all about specification. Manufacturer (Daihatsu) already specified DIII fluid as the fluid to be used in your transmission box. So the least you can do is follow the spec.

If you are a hardcore Petronas supporter and will not consider anything else, then buy only Tutela ATF DIII/D3. Alternatively, can use genuine Perodua ATF DIII.

Personal experience; I am using Lubegard Platinum in my Hyundai 4AT and Honda 5AT. Smooth drive all the way. Gone is the darkening (dark brown) or slight burn smell on both transmission. This Honda 5AT is known to konk out faster than local Honda 5AT as it is smaller (due to smaller available space taken up by bigger engine) and handle more torque.

Lubegard has also solved my Hyundai 4AT jerkiness on slow speed drive. This gearbox is nearing 300k kms now and touch wood still buttery smooth for a 4AT. ATF change interval also has been lengthened from 25k km (self imposed limit based on genuine ATF SPIII fluid degradation) to 55-60k km.

If you opt for Lubegard, you have 2 choices; Red or Platinum. Red is cheaper and is meant to be used with OEM ATF fluid spec. Platinum on the other hand is meant as a 1-stop solution for both OEM fluids AND if you want to change standard DIII fluid to high friction modified fluid like SPIII/Type-IV/Z1 etc.

Obviously from above, you don't need to change any fluid characteristic as your Kenari is using neat ATF-DIII. So you can save a few bucks by using Lubegard Red.

I can't speak for other additive brands as I have never used those b4. Lubegard has fluid viscosity like any ATF; thin and will not change the viscosity of ATF. Not sure about K&W TransX High mileage. As for Lucas Transmission Fix, from what I read, it is a very thick additive, so notsure if it will alter ATF viscosity.

Good luck.

Fortunately yes, can be bought from online malls. Just can't guarantee on authenticity coz this is Msia. Just focus on reputable, known distributors with online presence is safer.

Just an example

Dexron III ATF

Aisin AFW Fully Synthetic Dexron III ATF

Genuine Perodua D3 ATF
Lubegard

Lubegard Red

Lubegard Platinum

Unker.... no need to be too enthusiastic in changing out your new ATF that soon. Why waste the ATF if it is of correct factory spec? Wait till the next change interval lor.... as the car will be driven by your kids, it will pile up mileage soon enough.