Tranny Flush or Pan Drop?

I have a '99 Grand Prix 3.8L, non-SC. The odometer is showing about 120,000 miles. My brother bought it with 80k on it, I believe, and I bought it from him. Most of its miles are highway miles.

Now, should I assume that the most the dealership did to the car when it was traded in was check the fluid levels and clean the interior? (Everything on the car was original when I got it except for the oil filter, obviously) If this is a safe assumption, should I bother with dropping the transmission pan and installing a new filter? Or, is the transaxle young enough to justify shelling out $130 for a flush? I've heard on older cars that doing that can result in dislodging old sludge holding the transmission together, though that was usually told to me when asking about my '80 Caprice Classic.

And while I'm asking this, a few more questions. On really hot days (80-90F), my front driver's side window doesn't want to roll down. I don't hear any clicks or buzzing from the motor, just nothing. If it's cooler out (60-70F), then I don't have any problem at all. Is this a sign that I should look into replacing the motor? Also, how hard is it to replace the front passenger side quarter panel? I had a freak accident with a skid steer, which left a giant V-like dent in it.

As far as the trans is concerned it is not recommended to have it flushed. You are better off to drop the pan. I bought a pump from JC Whitney, and I pump the trans fluid out first. Then I drop the pan and replace the filter.

The other option is to install a pan drain plug like some of us did. That way you can let it drain out and drip overnight to get the maximum amount of the old ATF out. Regardless, in all cases the pan should be dropped to replace the screen filter and clean all the crud to include fine metal shavings out of the pan and clean the magnet. Some shops that flush do not necessarily remove the pan and replace the screen filter as part of the service for their cost. Even the fluid exchange servicer manufacturers like Wynn do not recommended flushing a high mileage transmission.


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