Don't need to overhaul the gb.

During your said shifting, the transmission control valve (metallic and male) was momentarily getting stucked within the valve body (metallic part and is a female) due to impurities.

The impurities or dirts/contaminants was from a 'used and burnt' ATF, at 70K km mileage in your case.

It is not caused by ATF leaks at polymer oil seals which hardened over say, 300-500K km usage. Oil seal hardening in a 70K km AT operating in low temperature regime is, imo academic.

Hence there is no need for ATF treatment (as recommended above, with due respect).

The only thing to do is:
replace new ATF. Period.

For mineral ATF type, replace new every 40K km or below.

For fully synthetic type ATF, replace new every 100K km or below.

*Lifetime fluids classification is a Mazda (and other car manufacturers) marketing terminology, It's not a technical or lubricant terminology.

*Mazda meant lifetime as manufacturer warranty period of typically 100K km.

Note: Don't ever do ATF flushing (with due respect) in a Control Valve System that always comes with super duper tight clearance at say, 1-5 microns.

1 micron = 1000 nano.

Just my 2 sen.

This post has been edited by zeng: Jun 29 2025, 11:41 AM

Yes, flushing can get near 100% of old used ATF fluid out in one go whereas typical 'drain and fill' cannot and like you say some 60% in one go.

Hence typical 'drain and fill' ATF fluid change (which may not be possible by oe design in Mazda) may need more 'goes'.

However typical workshop has another method in 'pneumatic extraction and fill' which would get out say 90% or thereabouts of old fluid in one go. Of course one can go for 2 'goes' or more as desired.

Besides, flushing method in ATF fluid change in North America has resulted (statistically) in more cases of AT problems than the 'drain/air extraction and fill'' method, probably due to violent and uncontrolled fluid agitation in flushing method whereas the other method is of much lesser violent fluid agitation, I guess.

This post has been edited by zeng: Jun 30 2025, 12:01 PM