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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.

  • If it's not broken, don't fix it. You'd be surprised how many new parts don't work off the shelf. – Dan Mantyla Feb 28 '18 at 17:53
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tldr; Other than peace of mind, no.

A '97 Blazer should have the 4L60e transmission in it. These transmissions have their known issues, the main one being the sun shell liking to separate near the hub. While the shift solenoids are not weak, these too can be a problem, but I'd suspect you would have seen issues with them well before now if you were going to see anything.

As far as the shift solenoids go, these are something you'd want to look at when you get the transmission rebuilt. It would be a peace of mind option, but something I'd highly recommend. The thinking here is since the tranny is all apart already during a rebuild, it's a really good time to replace these items so you don't have to look at doing the work until another 250k goes by.

With that said, 250k miles on a 4L60e transmission is a lot of miles. Knowing this, you probably want to plan on getting it rebuilt prior to something catastrophic happening to it or having it break down on you just when you can least afford it. You don't want to have the vehicle leave you stranded somewhere. If you have it rebuilt on your time, you can check this off your list of concerns. Most reputable rebuilders will ask you what you want put into your transmission. It's at this point you'd want to tell them to put new solenoids in it if they haven't suggested it already. Solenoids aren't that expensive, it's the labor putting them in which will cost you a few dollars.

As it stands, I wouldn't go out of my way to replace them unless they are exhibiting issues. Really, though, if you are having issues with your solenoids, other issues are right around the corner (if not present already).

  • Also consider keeping the old solenoids if they are good and you do your own work, they may come in handy. – finleyarcher Feb 28 '18 at 17:23

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