Change the fluid every 5 years or 75,000 miles, which ever comes first.

 

I only have them drop the pan, change the filter, and fill. I do not let anyone do a transmission flush, just based on the one time I did (99 Buick Century with 75k miles, that ran fine, just wanted to be proactive), two weeks later the trans crapped out, and had to be rebuilt. I'm sure others will disagree about this, but once it happens to you, you don't forget it!

 

This is related to a different brand car, but my Mom's Honda Accord developed a hard shifting problem around 170,000 miles. The fluid was brown and it smelt awful. I took it to the dealer and they recommended a flush. It made me nervous at first, but I gave them the O-K to do it. They had to flush it THREE times to get all of the garbage out, and when it was all said and done, the hard shifting went away. She's put almost 8,000 miles on it since the flush and it's still doing great. That was the first transmission service ever on that car.

I wouldn't flush your transmission because IMHO, it's not necessary unless you develop shifting or other related problems. If you do the pan drop and refill when you're supposed to do it (normal service intervals), you should never have to flush it.

 

I don't believe you have a pan to drop or a filter to change on your 2009.

 

I read that you need to drop the pan, change the filter and remove plug on the side of the trans and add Dextron III until it starts to leak out of the hole and then replace the plug into the hole and that is considered topped off. Does that sound right ?

 

............ and add Dextron III until it starts to leak out of the hole .......... Does that sound right ?

You may want to confirm that it takes Dexron III rather than Dexron VI. Dexron VI was out for the 2006 model year and I think most GM vehicles were specifying Dexron VI at that time.

Dexron III is no longer licensed by GM so technically it has not been made since 2006. Some vendors now market fluid suitable for transmissions specifying Dexron III, but technically, it is not Dexron III. Dexron VI is backward compatible so it can be used in cars specifying Dexron III. However GM says Dexron III can not be used in transmissions specifying Dexron VI.

Note: Allison says not to use Dexron VI in the older 1000 series that originally specified Dexron III. GM says just the opposite.

 

Now I see that the auto trans 4T45-E for 2009 & 2010 uses a filter but the 6T40 and the 6T70 do not.

The 2011 trans do not have a trans filter to change.