On the Transmission operating temp I am typically seeing 160's I noticed it was at 167f the other day on a long highway trip where I was running 75 to 80mph for a hundred or so miles. My 09 has a drain plug in the trans pan. At 200k it still looked pink but I drained what would come out of the trans pan drain plug (approx 10 Qts) and replaced it with new Dexron VI. From what I understand a 2ML70 trans has a overall capacity of 13 quarts so just using the drain plug swaps out the majority of the fluid. Figured since it looked pretty clean that it had been changed out by the previous owner. I had some clunky / jerky semi stall type issues before I recently changed the Hybrid Battery now it is a really rare occasion to have anything noticeable but I think with the complexity of the system it is going to have an occasional hiccup. If you are having some weird issues first check the 12V battery under the hood it good there then have the Hybrid Battery checked. The typical scenario of the semi-stall/clunk/jerky motion is when the Hybrid battery has reached end of life. It cannot reliably supply enough amperage to run the electric drive motor and turn the engine over to start it quickly enough to avoid the hesitation (semi-stall) The Hybrid battery packs last a long time but mine at 10 years old and +200k was just used up it was at around 23% of original capacity. Most likely most owners with old and high mileage is in about the same shape if not worse. Problem is the GM Two Mode system is a discontinued model since 2013 so the New battery packs are hard to find and very expensive. The companies out there refurbishing these Two Mode packs are relying on old batteries that they test to match up, you are probably getting a refurbished pack that is around 50% of the original capacity. Hopefully the Quantam Glass battery technology will be perfected in the next few years and we can step away from the these Nickel Metal Hydrid units.
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right side is sample of fluid before changing off the dipstick, left side is new fluid from container.
