faulty shift solenoid or bad transmission?

I can see why you are getting the solenoid error. I would have to agree that, at least, the solenoid pack for your second/reverse is shot. But — and there are several buts here — there’s a lot more going on, going back to the point where the dealer did the flush.

Of course, you should have the transmission fluid drained and replaced according to the schedule in the owner’s manual. The factory knows how long the fluid will last in the crankcase and, of course, it has to be replaced then.

With that said — and here’s the first but — your dealer had the transmission flushed. Usually, the shop will put a high-pressure hose on one side and blow in a lot of air to clean things out. In a perfect world, that would be the best way to go, but, the high-pressure blast not only strips everything out of the transmission but it can actually damage some of the more delicate components. You probably want to know how this happens and it is simple, the blast picks up all of the good stuff and the bad stuff, like any deposits that may have built up (they can be about as solid as cement) and will blast them through the interior, damaging everything in their path, like turbine blades, clutch packs and anything else. You just can’t tell the depth of the damage. Had the dealer just drained the transmission and then removed the transmission cover plate on the bottom, you would have been a lot better off as everything would have drained away. It is slower but it is safer.

Your dealer said there was an internal problem that caused metal filings to build up. That may be true, but, what caused the shavings to form in the first place? The chances, in my opinion, are very good that when the flush occurred shards of deposit slammed into small parts and damaged the parts, ripping off small pieces of metal which then fell to the bottom of the crankcase and which were then captured by the slightly magnetic transmission pan bolt (it usually captures a lot). Again, the flush started the problem, in my opinion, that is now showing up. In fact, I think it also caused the solenoid failure because of stuff that was dislodged and which may then have relodged around the solenoid itself (there are two, one internal and the other on the valve body casing — I’m talking about the interior one).

Of course, it may not have caused the solenoid failure in this instance. It still could have been part of the failure because a sensor may have been damaged and that damage may have put faulty signals through to the solenoid, causing it to fail. (It’s another but.)

Then, of course, the flush may have stirred up enough gunk from the bottom of the pan to cause one or more of the check valves in the valve body to stick. If that’s the case, you will not only lose the specific gearing to which the transmission fluid was being directed through the valve body, but (another one of those things) it also may have caused further damage as there may have been too much transmission fluid being pushed though one or two gears, while other gears may have been starved for fluid, causing more damage.

I think, by now, you get the drift of my idea. The flush that the dealer pushed through your Equinox’s transmission was like dropping dynamite into a closed space and covering it up tightly. The only result of something like that is basically taking what might have been a relatively easy event and turning it into something a lot more severe.

Overall, though I honestly don’t like saying this, I believe your transmission has failed. I wish it was just limited to the solenoids as they are a relatively inexpensive fix. That said, the flush likely caused a chain of failure within the transmission that has resulted in your Equinox’s need for a rebuilt transmission. It will cost about $3,400.

Here’s a thought: why not show this answer to your dealer and then ask what he will do to help you out with the repair. If he offers to cut the bill by 10 percent, you know you are on to something, however, be aware that dealerships routinely will “give you a break” of about 10 percent to make it appear they are helping out a lot — they’re not really. The reason I think it’s a positive is this: it opens up the whole topic of the dealer contributing a lot more to the replacement of the transmission which was likely messed up by the flush. Flushes are never a good idea, unless the transmission is new or extra clean because there is just too much chance for error.

I would keep pushing the replacement idea with the dealer. If you would like he can contact me through the http://www.transmissionrepaircostguide.com and I’ll be happy to help with this. I am happy to help.

As to who you should listen to, I think you can see which way my thinking lies. Your mechanic is a great source of information about your van. I’d listen to him (or her) first.