Replacing a 4 speed auto transmission in 07 Aveo

My wife has gingerly cared for and driven her 07 and loves it dearly.

200k miles is upon us and we have replaced all suspension parts, the break hoses and calipers, valve cover gasket, transmission filter, and battery terminals. Maybe more, but the point is that the body, frame, suspension and most of the engine is in great condition. Starts up and sounds nice and we've always been on top of the oil changes as well as the previous owner.

The only issue is that the transmission fluid is black and even after a filter change the car lugs and has issues shifting when she drives more than a half hour.

We are going to buy a manufacturer rebuild from the near by Chevy dealership for $2,500 if we can read about how to swap the transmission. We have a PDF manual, but I haven't had much time to look since we've made this decision.

Does anyone have advice/experience to help guide us?

I would not replace the transmission simply based on the 2 symptoms you described, because neither of them eliminates the engine as being the problem. And black fluid does not indicate transmission failure, unless the fluid smells burnt, or there are metal fragments mixed in with the fluid.

At the very least I'd want to scan for codes, using a reader capable of reading the TCM. If nothing helpful comes from that, then additional diagnosis using a realtime data stream reader would be my next step.

Thank you for your reply! Do you think the Blue Driver scan tool will be sufficient?

Yes that would work, but I believe Torque Pro for Android is just as good for a lot less $$.

Do either provide live information?

Yes, they are both realtime OBD datastream readers.

I found a bunch of small blue translucent modules with different names. Most are $12 does that sound right?

Yes, I assume you're looking at Bluetooth OBD dongles, and then you would also need to download the Torque app to your device.

Is any dongle appropriate? They all say ELM 327, but some are large and black with lights and others like I said small and blue. Some day HH OBD2. I just don't want to buy the wrong one and have to buy and wait for another.

You need to compare the specs provided for the dongle, to make sure it's compatible with the device (phone, computer) you will be pairing with it and using to read the data stream.

200k is a lot of miles for the AW81-40le trans. Mine did the same at 100k. Every trans shop wanted 3k to rebuild it. Ridiculous. I ended up buying a used one (22k miles) off eBay for $400 shipped. Just saying it may not be worth rebuilding when you can get a low mileage used one for next to nothing.

So you were right to try the obd reader. The code would reset by the time we got home. We have a cylinder one misfire.

Here's the deal. All but one spark plug was soaked in oil and we already replaced the valve cover gasket.

I'm worried it's piston rings.

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Originally Posted by dbooyah93

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Here's the deal. All but one spark plug was soaked in oil and we already replaced the valve cover gasket.

I'm worried it's piston rings.

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I'm assuming you're saying that oil was on the plugs above the threads. If so, there are a few ways to mess up the VC gasket install (primarily torqueing incorrectly), and that would be my first suspect. When replacing the VC gasket you should use an (inch) torque wrench and tighten the bolts incrementally and in proper sequence. And also use (a very small amount of) RTV only at the transition points.

Did you also replace the plug wires? If not, a plug wire is highly likely to be the cause of the misfire.

There was oil ABOVE the threads AND below.

We saw that the cables looked poor inside them where the connection is made.

We will replace wires too. Thank you

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Originally Posted by dbooyah93

There was oil ABOVE the threads AND below ....

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Yes, oil on the threads is expected because it quickly runs down from the pool in the plug well as the plug is being removed. IMO you have no need to be concerned about any issue other than the VC gasket and the plug wires.

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Originally Posted by avguy

Yes, oil on the threads is expected because it quickly runs down from the pool in the plug well as the plug is being removed. IMO you have no need to be concerned about any issue other than the VC gasket and the plug wires.

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We replaced spark plugs, and wires after cleaning tubes. We no longer are getting the misfire. We will check for the leaking oil later, but the VC was torqued to spec

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Originally Posted by dbooyah93

Â…. We will check for the leaking oil later, but the VC was torqued to spec

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There's really no explanation for oil above the plug threads, other than a bad VC gasket seal, and if the job is done correctly, the plug wells will remain completely dry for years. Did you tighten the VC bolts according to the 'book' sequencing, using 3 passes (or at least 2), with a final torque somewhere around 100 inch-lbs?

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Originally Posted by avguy

There's really no explanation for oil above the plug threads, other than a bad VC gasket seal, and if the job is done correctly, the plug wells will remain completely dry for years. Did you tighten the VC bolts according to the 'book' sequencing, using 3 passes (or at least 2), with a final torque somewhere around 100 inch-lbs?

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So we put the VC gasket on about 10k miles ago. Can we reuse it, or should we get a new gasket? Can we just loosen the bolts, and tighten them in the sequencing way that you are referencing?

Definitely buy a new gasket (Felpro makes a good one) and do the job over from scratch. If you need the sequence numbers, I'll fish it out and post it for you.

Quote:

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Originally Posted by avguy

Definitely buy a new gasket (Felpro makes a good one) and do the job over from scratch. If you need the sequence numbers, I'll fish it out and post it for you.

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I bought a felpro gasket, thoroughly cleaned all surfaces. Torqued up to the textbook instructions 90 (~10Nm). As specified sealant on the correct areas.

Again after about 3000 kms leaking on the corner.
These are such a pain for leakages.

Maybe I should have put sealant all around.

Should I attempt to tighten it up a bit more or would that make it worse now the sealant is cured?