Eric777

Ok guys. One more question. I understand somewhat the procedure for refilling the transmission. Do you let the extra fluid out of the overflow while the engine is running?

Doublebase

The fluid adjustment needs to be done with the car running (in park) and you should only pull that drain plug when it has reached the transmission temperature parameters. Once it is in temperature range (I believe it’s between 104-112 degrees), pull the drain plug and let it drain until it comes trickling out in a light stream. If it’s overfilled it’ll pour out. If it’s underfilled you’ll have nothing coming out (and you’ll need to add and do the temp check over). I can’t stand it when I screw it up and underfill it because it makes me have to do it twice.

UDel

Is it really that important to match temperatures, drain/fill it while it is hot/certain temp? I have never heard of that for other cars, not that I really researched it but most people I talk to who do it just drain it while it is cool. Just sounds like a lot of extra work, extra problems.

thallium

Cars with a dipstick require you check the ATF when the car is up to temp with it idling. Since these cars don't have a dipstick it adds levels of complexity given that you have to have the car in the air to check the fluid and it's not as easy as being able to fill from the dipstick if you're too low. It's a one-and-done fill and check and if you get it wrong and the ATF gets too hot, especially where I live in Phoenix you may have to wait 24 hours until it can cool down enough to check again. It would be dead simple to check the fluid and fill if necessary if Toyota had put a dipstick but they didn't.

JeffKeryk

The top of the atf is the same regardless. A dip stick or sight hole makes no difference.
If temperature was so critical, why didn't Lexus put a temp value on the display?

I love our GS and plan to keep it for a long time. Regular services are a no brainer to me.
And don't get me started on 10K oil changes... Ha!

thallium

I assume as it heats it expands and there is a way to read the temp. Jumper pin in the OBD port and certain movement of the shifter in and out of park. It will notifiy you when it enters the lower threshhold and when it reaches the upper threshhold with certain flashes of the drive mode on the dash.

UDel

Trans dipsticks are normally pretty difficult to get a good reading, especially on a longitudinal RWD car with the trans further to the rear and the dipstick being angled so much and traveling so far, I could never get a good reading on my 2nd Gen GS430 so I just replaced what I drained out, that is what many do when doing a drain/fill because it is a big pain if you over fill it/difficult to get a good reading anyway on many cars. If you just put in what you take out whether it is hot or cold it shouldn't be a problem, even a little difference should not be a issue either, there has to be a margin of error built into the capacity. The whole matching temps is just very odd, sounds needlessly difficult, no shop is going to want to do that so that is probably why many refuse to even consider a drain/fill on the 4th gen GS350. I doubt in other markets the techs are matching temps of fluids when doing a drain and fill. Very few DIY'ers are going to want to do that or would even know about it. What changed in the design from previous GS's where you don't match temps on a drain and fill to the newer one aside from lack of dipstick which was never easy to read anyway?

thallium

I assumed it was solely due to lack of dipstick but I'm not sure what Gen3 GS's have though they probably have no dipstick either and would require the same procedure. I have a 2007 V6 Camry that had shifting issues so did several drain and fills and I had to use the same fill and check procedure with the temperature. I'm sure there is a margin of error that's why the temp range is like a 104 to 113 or close to that. Don't dipsticks have an acceptable range that would account for heat expansion too? I'm also not sure how much the volume of fluid could change over 10 degrees. I can't imagine it's that much.

JeffKeryk

I am referring to a readout on the car's infotainment screen. I can read the transmission fluid temp with an OBD II interface and a cell phone app, which is what I do.
Why don't they just make these values available on the car's display? It's just a little software. It's harder to display the tire pressures, which they aleeady do.

thallium

I agree, they should make it available and I'd also like actual degree values for oil, coolant, transmission and actual battery voltage but I'm sure they have decided that the vast majority of car buyers neither care nor would make use of them so why add to the cost of the car in either mechanical gauges or coding for a digital display. From my point of view, why not make more information available to the user when the cost would be so minimal.

BTW, I when I did my ATF drain and fills I compared the OBD pin temp check, my OBD scanner reading and an infrared thermometer reading of the pan and here's what I found.

I was operating under the impression that the OBD jumper pin method indicated temps 104-113 F. I have no way to verify that and don't know where I found it now but in any case the temps are in the order of: lower threshhold / upper threshhold by the method of the reading.

• OBD jumper pin: 104 / 113
• OBD scanner: 120 / 128
• Manual pan temp: 106 / 115

Knowing this could allow you to just use the manual pan temp to tell which is much quicker and easier than either of the other methods. I'm not sure what the differences between the OBD temps are but I guess the sensor I'm accessing in the OBD software is not the same one used in the jumper pin method.

Eric777

So I changed the tranny fluid today. I bought this car used with 119k. All dealer service was performed, of course that say you don't need to change fluid. Yeah, right. I pulled the pan also. Sludge in pan, oil looked like dirty motor oil. Sure glad I changed. Think I'll do a spill and fill again soon. My opinion, change it. Yes your motor oil gets dirty, but that is internal combustion engine. Don't need that crap clogging ports, solenoids, etc.