1999 Lexus LS 400 • V8 2WD Automatic • 145,000 miles

I have a 1999 Lexus LS400. I bought it used and now has 145,000 miles. It doesn't appear that the transmission fluid has been changed. Firestone is advising me not to change it because the pressure in the transmission is too low. They say that by changing it, the transmission may not work or start to slip. Any comments?
Fred Castellano
February 21, 2011.

If it is really dirty, the new detergent in the ATF will clean the dirt from the clutch plates. That "can" cause a slip. However, I have never seen it actually happen.