While we are on the subject of maintenance intervals for trans-axles I would like to ask if anyone has experience regarding cooling system maintenance on the GXPs. I know the owner'* manual indicates the interval for flushing the cooling system is 150K or 5 years. The 150K seems a little optimistic to me. Can you really expect a Dexcool system to go this far without corrosion occurring?

From what I remember, dexcool should be replaced every 100k, or at least that'* what the recommendation was before. I had mine replaced at 50k during service of the water crossover gaskets, but I really wouldn't take a chance goin 150k with the factory coolant fill considering its an all aluminum block with aluminum heads. I'd get it done at 80-100k if it hasn't been done during replacement of the water crossover gaskets.

Where is the second trans drain? Is it inside the pan or outside? I asked the tech when my car was getting done 2 weeks ago, 41K mileage. He didn't know of a second drain.

I didn't find a second drain either. My filters were actually "screens" and there were two of them. It drained something stupid like 8 quarts. I was amazed.

The recommended service interval on the transmissions is only 60K. And per GM and many other manufactures, you cannot determine how good the fluid is based on color. Just because it has darkened, doesnt mean its bad. And just because its still pink/red or even an orange tint doesnt mean its still good.

Hell, based off of Motorist Assurance Program now, at work I cannot recommend a trans service based on fluid color and smell alone.