Replacing a 4 speed auto transmission in 07 Aveo

[dbooyah93]

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?

[avguy]

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.

[dbooyah93]

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

[dbooyah93]

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.

[avguy]

…

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.

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.

[dbooyah93]

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

[avguy]

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

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.

[avguy]

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

[dbooyah93]

Do either provide live information?

[avguy]

Yes, they are both realtime OBD datastream readers.