99Silverado half ton 46,000 94 Suburban 95,000 it has been changed at dealer but last time i dont think they touched it? Silverado has never been changed,easy driving on both what should i do???

I would change them both, just due to age.

Plus the newer fluids are quite good, and if you can do it yourself, the cost isn't that bad at all.

I would do a pan and filter sevice on both. After I would perfrom a cooler line fluid exchange with some Supertech Dex VI. I have had very good results with the older 4L60E/65 transmissions when going from DexIII to the new Dexron VI. You will need about 14-16 quarts to get most of the old fluid out.

I agree with the Arizona guy. Drop the pan and change the filter. Especially on the Silverado that has never been changed. Some 75 percent of the contaminants/wear debris in the life of an automatic (per Eleftherakis & Khalil) are either present at birth (manufacturing debris) or come from break in, so the first change is the vital one. This should happen by 5K miles. Also, install a cooler line filter, such as a Magnefine, installing it on the return line back into the trans.

Agree with both AZ guy & Jim. I'd add one thing. If you follow Jim's good advice...this applies ONLY to a new vehicle...you would want to install the Magnefine on the line going from the A/T to the oil cooler(s). If the in-line filter is first installed AFTER about 5,000 miles, you'd do as Jim states and install it on the return line.

Sarge,

You know that you will have to explain yourself as to why you recommend installing a filter in a cooler supply line when new & cooler return line after ~ 5k miles. This makes absolutely no sense to me.