Have a 2005 Gx470 with 212k on it. As soon as the vehicle is moved from idle, it immediately shifted through the gears until it was in 5th gear at 30mph. At 45mph, it was screaming at 4500rpm. I looked on my scanner data and noticed that the SPD reading was at 65mph when the vehicle speedometer read 30 mph. Also looked at the vehicle speed PID and it matches the instrument cluster. I changed out both speed sensors. It shifts just the same, in 4th gear by 25 mph and high revs. This time however, the SPD pid closely follows the speedometer. The kicker is that there are no codes in the ECU or TCM. Any suggestions?

 

Did you do a computer reset?
Pull the negative off the battery, wait about 2 minutes, then reconnect with a minimum of sparks.

You will need to calibrate the auto-down windows, auto-open sunroof, radio presets, and seat memory afterwards.

Chip H.

 

I did do a memory reset with my scanner and then drove the 15 minutes necessary to relearn the shift values. No dice.

 

You describe symptoms as quickly shifting up in gears despite low speeds, but also high revs at low speeds, which would indicate it's still in low gears when it should have upshifted, doesn't make sense to me. Any chance you could explain better what's going on here?

How are you determining that that trans is shifting up in gears? Are you able to confirm what gear your trans is in at a given moment via your scanner or something?

What would happen if you put the shifter in the "2" position and tried to drive like that?

 

I am able to tell what gear it is in by looking at live data on the scanner. The one thing that I noticed driving it this morning is that the Lockup Solenoid is always Off, the SLT solenoid is always On, the SLU solenoid is always OFF and the Overdrive Cut Switch is always off. These never change no matter what driving condition. If I manually put the vehicle 1st, 2nd, 3rd or 4th, the appropriate gear would show engaged. I assume that this vehicle does not have a manual O/D on/off switch like other vehicles do so could not test that. I believe that this is an unrelated issue but i will mention it anyways. The other thing that I noticed is that the vehicle felt like it was dragging. I let my foot off of the accelerator and it would immediately slow down even if i switched the vehicle into neutral. After a bit of driving I started to smell the brakes and found that one of the front rotors was at 450 deg while the others were below 200 deg. But again, i dont think that a sticking caliper would cause the trans issue.

 

As I described, from a standstill, i let my foot of the brake and press on the gas, it is in 2nd gear, then instantly goes into 3rd, and by the time i am at 20mph, it is in 4th. There it will stay no matter what higher speed or rpm. Im driving 40 mph at 4500 rpm. I got it to go into 5th one time where the rpm dropped down a little but never got it to go into Overdrive. Again, i can watch live data and see what gear it is in at any given time.

 

I don't have hard numbers to support this as I type it, but 4th gear at 40mph should NOT be at 4500rpm. That sounds to me more like it's stuck in 2nd or 3rd gear, even though the scanner shows 4th.

This is one you might want to bite the bullet and let the dealer diagnose...figure out how to proceed from there.

 

I can feel the shifts as i am watching the scan data. It is definitely in 4th gear. I just found a diagnosis chart that i will see what i can find out. It was telling me to check both of the speed sensor circuits, which i changed out the sensors but didnt check the wiring, check the SLT solenoid, L4 solenoid, throttle body data and ECM. Think i will start with the SLT circuit since i can see that it did not do anything but stay on no matter what the driving conditions were.

 

Ok people disclaimer time. Nothing aggravates me more than researching an issue on threads and reading all the discussion but then the original poster doesnt post what the final solution is. Well, i figured it out. Not being familiar with the GX series of Lexuses, I figure one AWD vehicle is like the others. I went on another test drive and looked down at the center console and was hit with a baseball bat at the epiphany. There in front of the gear shifter is another shifter for the 4WD to move it from H to N to L. And boy how it looked like it was pushed forward to Low. Put it in High and away I go. Transmission worked just fine. No wonder there were no codes DUH!!!!! I will now go put on my helmet and disappear on the little yellow short bus and solve the other issues this vehicle is having.

 

Yep.
That would do it.

Glad you figured it out.

Chip H.

 

That explains the high revs for the low speed! Glad it was an easy/free fix aside from your time!