Lincoln/Mercury Repair: Coolant and Transmission Flush, slipping transmission, transmission overhauls

Question
Hi, we recently bought a 2002 Lincoln Navigator with 60k miles.  We had the oil changed at the dealership and I was going to have the transmission fluid changed there but found out it was going to cost over $150.  Now reading some of the questions you have been asked and your answers - do I really need the transmission fluid changed?  Also they said the coolant needed to be checked, is that something that is easy enough to do (just drain and add a gallon of coolant and the rest water?), if so do I look for the drain tube like most radiators or is it some where else. please advise.
Thank you!!!

Answer
Hi Anna,

As you might have suspected, in real life, I manage a Cottamn Transmission shop in Las Vegas. I could actually change the fluid in my transmission everyday for free. I now have 113,000 miles on the original fluid. I have never changed it. I have learned over the years that a tiny percent of car owners will change their transmission fluid on a regular basis and that's fine. If you do it regularly. When problems start is when folks let it go for 30,000 plus miles and then try to do the right thing by changing it when it's too late. What I mean is there is a condition that developes in transmission fluid we call varnish. Once varnish has become present in the transmission fluid, it must stay there. If we change the fluid it will rinse that varnish out and within a couple of weeks your transmission will start to slip. There is only one cure for a slipping transmission, overhaul. Half of the transmission overhauls we perform is due to folks changing their fluid when it's too late. So in a very long about way, I am trying to save you from a heartache and advise against changing your fluid. Oh, and don't worry about a clogged filter. By the time a filter could clog you would be far beyond needing your transmission rebuild.

I would have a repair facility that you trust change the coolant. It holds much more than a couple of gallons due to the rear heating system. I think I read 5 gallons! I am a bit more agressive with my mixture. I am about 80%. I used to live in NH where it could get to -40. Now, here in the desert it gets to 125. Hope this helps, Enjoy your Lincolns, the only cars I own.