In my reasearch, I have found MANY mentions of NOT flushing if the fluid is already completely broken down (brown in color and STINKS!). For some reason, within 500-5000 miles after a flush with completely burnt fluid, trannies tend to fail. So, "spot" check the fluid first. Get a clean quality white paper towel and set it on top of your UIM. Now, pull up the dipstick and dab 3-5 spots on the towel. If it creates a "bulls eye" with a brownish center, don't flush it. If it creates a uniform pinkish blob, it's safe to flush ... again, this is what I have read, not what I have done.
