Transmission Fluid

pappastratos · October 18, 2010

I have a 2001 recently purchased RX300. 120K miles, appears trans fluid has not been changed. Smells fine, but is dark.

Car salesman once told me that if the trans fluid has never been changed, don't change it. Because that new fluid has strong cleaners & it will cause problems. Could I clean catch the old fluid, replace filter & add old fluid back ?

Filehorse · October 18, 2010

The reason the guy who told you that was a salesman is likely because he didn't have a clue about working in the Service Department. First, your "filter" may not be a filter at all but a screen. The one on my 2000 RX300 AWD is like that. I was going to purchase a new "filter" but the guy at the Lexus parts counter said what they do is simply remove the screen and flush it with a solvent (I used straight mineral spirits); blow it dry and reinstall it. There are no paper/fiber "filter" components in my screen. Replace the drained fluid with new T4 ATF or equivalent. There are additives in there which do wear out and you're only going to replace maybe 1/2 the fluid anyway. What the salesman may have been referring to is to not perform a "flush" procedure whereby they actually use a pump to displace all the fluid in the system including the torque converter and the ATF cooler. In a high-mileage vehicle, this can dislodge accumulated sludge in the system and create problems that you don't want. I am convinced this is what happened to a Jeep Grand Cherokee Limited (115,000 miles at the time) I owned. The transmission failed catastrophically within 1,000 miles of flushing the system and it was performing flawlessly prior to that failure. At the time of disassembly, the technician told me the ATF cooler lines were almost completely plugged with sludge. I've never heard of a similar issue where the ATF was simply drained and refilled. What I do on my RX300 is drain the fluid; remove and clean the screen; reinstall the pan with a new gasket; and refill with T4 or equivalent ATF. I will then drive the vehicle around for 10-15 miles and then drain the fluid again without removing the pan and then refill as specified. This should replace at least 3/4 of the original ATF and the second drain only takes a very short amount of my time.

Of course, your mileage may differ.

Lotsa luck.