Hi Guys!

260K Miles 2008 HHR 2.2.
The tranny is "okay", I get a small knock in 2nd gear but smooth in all others. Going reverse is also smooth.
My main issue is a possible torque converter going bad as I get a weird RPM surge around 40-50mph.

The tranny oil has never been replaced. Don't hate me, I just got the thing!

Will I open a can of worms if I replace the oil?

Thanks!

 

The ATF is Lifetime, unless extreme use. Change it if you want to. Don't get a flush and fill. Make sure you use Dexron VI. I doubt the surge has anything to do with the torque converter.

 

The 40 mph surge can be TCM related. Kinda common.

 

By small knock you mean spark knock, not driveline noise, right?

I have a 2010 Buick 3.6, 91 octane “recommended.” It does lurchy things like that if fed regular. Or not, seemingly depending upon the (unknown) quality of the regular fuel. I attribute it to the knock sensor complaining, causing the ECM to roll back the ignition timing at moments inconvenient for the transmission.

Even tho your 2.2 is supposed to be fine on regular, could try a tank of 91 or 93. If it seems to make a difference, you could question your source of fuel, or look into other causes of knock like carbon deposits (Lots of short trips? Black soot in the tailpipe?) Wrong spark plugs?

Does it misbehave all the time, or when the engine is hot, or cold? Does it change with the weather or after a fill-up? If you think there could be carbon deposits, you could put some detergent additive in the fuel.

What ever happened to “Top Tier” fuel? I can’t find that sticker on pumps anywhere around here anymore.

My 2008 HHR 2.2 didn’t knock, but would lurch or surge sometimes like you describe. I just learned how to use the gas pedal in ways that it didn’t.

 

guy, 260K is way too much..
no matter what, change the transmission fluid, it will be useful in any case, at the same time you will look at the condition of the transmission oil.
And yes - Dexron 6!
And yes, the filter needs to be replaced too. Buy a new filter, give preference to the product with the gasket included. Make sure that the gasket has a steel frame, another gasket only creates problems when replacing. Also remember, the bolts must be tightened evenly otherwise the transmission fluid will ooze through the least tightened spot.
For reference: the manufacturer promotes the entire service life without replacement only because he means the average service life in laboratory conditions, which has nothing to do with real life. In addition, the failure of your automatic transmission is in favor of the manufacturer, he gets a chance to get your money for repairs in one of his car dealerships or even for a new car. Desire is understandable, but hardly meets your interests.
Experienced owners recommend a preventive transmission fluid change every 60 to 80 thousand km (40 to 50 thousand miles)