We often get asked how often should I service or change the fluid in my 4l60e? Often, anywhere from 30-50,000 miles is acceptable, depending on usage. If your vehicle only sees highway miles, then you can wait to change your fluid when you are at the higher end of the spectrum.
If you see a lot of stop and go traffic, tow, or race, you should certainly replace the fluid in your 4l60e every 30,000 miles. If your fluid is dark and or has a burning smell to it, then it is past due, and you may have bigger problems on your hands.