Is there any maintenance advantage to replacing shift solenoids that have not failed? There isn't a stated service interval for these parts, that I am aware of.
By contrast, most vehicles have inspection/replacement intervals for the serpentine belt. My thinking is the accessory belt is a moving part, exposed to wear and high heat, and will 100% strand you if it fails while driving. Moreover, a failed serpentine can lead to compounding problems if the engine suffers prolonged overheating as a consequence, etc. So, for these reasons, it makes sense to replace them before they reach a state of failure.
Now if I transfer my reasoning about serpentine belts to thinking about transmission solenoids, and doing some reading, I learn this (emphasis mine)..
The transmission solenoid is responsible for opening or closing valves in the valve body to allow transmission fluid to enter [...] Solenoids consist of a spring loaded plunger wrapped with a coil of wire, and communicates with the car’s engine sensors or the transmission control module (TCM) via electronic signals to either open or close.
Sensors determine when it’s time to shift [...] If the transmission solenoid is energized, the plunger opens and allows fluid to pass while a solenoid that is not receiving power is closed in its normal position. So while the various engine sensors determine when the gears should shift, it is the job of the transmission solenoid to act out the actual shifting.
So these are moving parts that are exposed to wear and high temperatures. But can individual solenoid failures leave you stranded? And can a failed solenoid quickly lead to a compounded problem?
I am aware that the computer in modern vehicles can sense/calculate some solenoid issues and put the vehicle in "limp home mode". So solenoid failure may not necessarily strand you. But I don't have a concept for how rapidly a solenoid failure can encourage compounding issues.....sudden additional/unusual wear on old clutch bands, overheating? etc.
Right now my vehicle (97 Chevy Blazer) is driving fine and shifting fine. ::knocks on wood:: But at over 250k miles I am wondering about maintenance opportunities beyond the vendor's 150k mile service interval maximums. Thus my question about these solenoids.