Transmission Flush / Coolant Flush at 60k?

[Lux]

If, especially, Toyota Motor Corporation specifies intervals for clearly indicated maintenance services, there is highly likely to be profound evidence to support it. Toyota engineered your vehicle, not General Motors. Ethylene glycol coolant is organic by formulation, therefore it is susceptible to oxidise over time and use, eventually acidifying as the glycol base decomposes into acidic components. Corrosion resistance on metals, such as aluminium, will diminish. Genuine Toyota Super Long Life coolant is capable of extending the typical service life up to 100'000 km, but that is stretching a coolant's chemical tolerances. Want to see what happens to the cooling system components when services were neglected? Google DEX-COOL.

Transmission services should have been performed when scheduled to do so. Typically, these services are scheduled before the fluid becomes excessively contaminated by wet clutch friction material. When contaminated with clutch deposits, the fluid becomes abrasive, further accelerating wear. In foreign material blockage scenarios, wherever the fluid travels is where the contaminants would have been deposited. If your transmission fluid smells burnt and has a fine, grainy texture to the touch, it is overdue for a service, regardless of whether you have reached the interval. Severe hydraulic pressure, shock loads, and heat are natural environments for automatic transmission fluid, so it must be serviced regularly. Yes, it is possible to render a transmission unable to drive on its own power if the service is performed on an automatic gearbox that has suffered severe neglect. That is death by severe neglect, not new fluid. Aside from load or abuse, transmission design is a substantial factor in determining service intervals and total longevity. Some gearbox designs could outlive a century of driving with regular service. Others (Subaru, Fiat, GM, Chrysler, Hyundai) may not survive 10 years of normal use.

'Schedule' means to perform before or upon arrival of due time. Not when you feel like it. The same logic supports why other cars' timing belts are changed before their typical 96'000 km intervals.

Your manufacturer-supplied maintenance schedule needs to be adjusted according to severity of use, sometimes referred to as severe duty schedule. It is modified such that the intervals for every service other than oil changes are significantly condensed to account for harsher use. I would say that 90% of all automobiles in North America qualify for severe duty schedule. For instance, instead of the 192'000 km interval for spark plugs, mine are replaced every 30'000 km due to sustained high RPM use.