cruzn*k

Took my 1999 RX 300 in for servicing (45,000 mi) and the mechanic replace the transmission fluid with Mercon 3. Is this okay or should he have it replaced with T-IV. This was not at a Lexus dealership. Mechanic is ASE certified and so called Lexus expert.

If I need to replace it with T-IV, must the trans filter be changed and the pan taken off to drain all the Mercon 3.

salimshah

The mechanic needs to prove to you that
a) Mercon 3 is equivalent or superior to Toyata T IV
b) Mercon 3 and Toyoato T IV can co-exist.

I did a quick search and could not verify "a" above.

Trans fluid after shut down of engine exists in the following places.

1. Hoses and chanmbers on the high side of the pump.
2. Torque convertor.
3. Chambers of the transmission.
4. Stuck to various parts of transmission rest trickles down under gravity.
5. In the transmission pan.

By dropping the pan and the filter you will get part of 4 and mostly 5. By doing a drain you only get 5. [1-2 table spoon difference between the two ... assuming you have the wire mesh oem filter]

You can opt for a flush [insist on the transmission pump to force circulation] and the rest of the hook up to just add and drain the fluid.

or

Do repeated drain and add. drive for 50 miles or so to mix the new and old.
After about 5 drains and fill you will get most of the old stuff out (70+% of new). If you do 11 drain and fills you get to 99.9% of new fluid. If the mechanic did a drain and fill, currently you have a mix of T IV and mercon 3. With 5 drains and fill you will 90%+ wiht Toyota TIV.


What the mechanic did may be OK, but this is the prime reason I either DIY or take to Lexus dealership.

Salim