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Hello all. It has been  a while since I posted here. The car has been very good until now. Two years ago, I had to replace the ECM with a rebuilt one, in order to pass state inspection. Recently, the shifting has been problematic. At lower gear, the RPM spikes up to 3500 RPM, at 20 mph and it seems that the car actually slows down to shift to a higher gear, my guess is from 2nd gear to 3rd gear. I contacted the guy who sold me the ECM and he sent me a newer rebuilt one. I just put it in yesterday. The fluctuation in the RPM started even at a lower speed on the newer ECM, at 10 mph. Then today, the problem associated with the previous ECM is happening with the newer ECM, the car seems would not move into higher gear, like from 2nd to 3rd, and the RPM spikes up, the engine is roaring but the car just would not go very fast. By replacing the ECM we had eliminated that the ECM is not the issue. I was told there could be the speed sensor (driver or passenger side, not sure which one) or one of the shift control solenoid. From the mechanic who sent me the ECM, there are 3 possibilities on the shift control solenoid but I am not sure which one. Here are the 3 part numbers:

85420-50020

35270-50010

35280-50010

Which one amongst these, is the most common and most replaced shift control solenoid? I could go into one of the Lexus dealer and talk to the parts department to find out from the manager but I think that is a long shot as they are probably reluctant to share that information with me. That is why I post this on this forum to gather polls from you guys. I may try to go into the dealership parts department tomorrow to try to find out.

The other possibility is the transmission is finally going bad. Years ago, I took my own ATF fluid to a mechanic for a transmission fluid drain and fill. I can  usually feel it will shift much smoother after the drain and fill but it was the opposite. Not sure what is wrong, so I immediately drain and fill like 4 or 5 times to get the fluid replaced. Perhaps I should do a complete fluid exchange but I did not do that. Perhaps the transmission is finally giving in due to possibly wrong fluid being used by the shady mechanic. Ture story, I asked a mechanic to install the Honda Odyssey transmission I bought, I brought him 4 quarts of ATF and ask him to use them. When I go pick up the car, I saw the same box of ATF sitting in the corner as I have to go use his restroom. I got those ATF back from him and never went back to him again. Cheap mechanic actually stole your OEM ATF fluid, just to make an extra buck, come to find out. The mechanic I used to do the drain and fill on the LS400 has since sold his business. Do you guys think the transmission is going out because the wrong fluid is used one time?

Your input and comment is most appreciated. I find these posts are very useful as I saved my totaled 2002 Mercedes S500, revived it back from the flood waters of Harvey in 2017 after I posted on another car user forum. I bought the car back from the insurance company, the dealer put a new battery in and Walla, the whole car is working normal again. I am hoping to have good results with my 1996 LS400 with 190,000 miles with new timing belt at 180,000 miles. I hate to see her go into salvage yard at such an early age. The transmission usually last about 300,000 miles? 🍺 Cheers and thank you.

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On 1/6/2021 at 1:21 AM, StructureEngr said:

Hello all. It has been  a while since I posted here. The car has been very good until now. Two years ago, I had to replace the ECM with a rebuilt one, in order to pass state inspection. Recently, the shifting has been problematic. At lower gear, the RPM spikes up to 3500 RPM, at 20 mph and it seems that the car actually slows down to shift to a higher gear, my guess is from 2nd gear to 3rd gear. I contacted the guy who sold me the ECM and he sent me a newer rebuilt one. I just put it in yesterday. The fluctuation in the RPM started even at a lower speed on the newer ECM, at 10 mph. Then today, the problem associated with the previous ECM is happening with the newer ECM, the car seems would not move into higher gear, like from 2nd to 3rd, and the RPM spikes up, the engine is roaring but the car just would not go very fast. By replacing the ECM we had eliminated that the ECM is not the issue. I was told there could be the speed sensor (driver or passenger side, not sure which one) or one of the shift control solenoid. From the mechanic who sent me the ECM, there are 3 possibilities on the shift control solenoid but I am not sure which one. Here are the 3 part numbers:

85420-50020

35270-50010

35280-50010

Which one amongst these, is the most common and most replaced shift control solenoid? I could go into one of the Lexus dealer and talk to the parts department to find out from the manager but I think that is a long shot as they are probably reluctant to share that information with me. That is why I post this on this forum to gather polls from you guys. I may try to go into the dealership parts department tomorrow to try to find out.

The other possibility is the transmission is finally going bad. Years ago, I took my own ATF fluid to a mechanic for a transmission fluid drain and fill. I can  usually feel it will shift much smoother after the drain and fill but it was the opposite. Not sure what is wrong, so I immediately drain and fill like 4 or 5 times to get the fluid replaced. Perhaps I should do a complete fluid exchange but I did not do that. Perhaps the transmission is finally giving in due to possibly wrong fluid being used by the shady mechanic. Ture story, I asked a mechanic to install the Honda Odyssey transmission I bought, I brought him 4 quarts of ATF and ask him to use them. When I go pick up the car, I saw the same box of ATF sitting in the corner as I have to go use his restroom. I got those ATF back from him and never went back to him again. Cheap mechanic actually stole your OEM ATF fluid, just to make an extra buck, come to find out. The mechanic I used to do the drain and fill on the LS400 has since sold his business. Do you guys think the transmission is going out because the wrong fluid is used one time?

Your input and comment is most appreciated. I find these posts are very useful as I saved my totaled 2002 Mercedes S500, revived it back from the flood waters of Harvey in 2017 after I posted on another car user forum. I bought the car back from the insurance company, the dealer put a new battery in and Walla, the whole car is working normal again. I am hoping to have good results with my 1996 LS400 with 190,000 miles with new timing belt at 180,000 miles. I hate to see her go into salvage yard at such an early age. The transmission usually last about 300,000 miles? 🍺 Cheers and thank you.

Is your check engine light on? Your car should be throwing some error codes and that would be a good place to start. Have you checked the transmission fluid level?

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  • 2 weeks later...

They say that the AISIN warner speced oil is different and to use the right one is important. Mixing different ATF where one is wrong is also a bad idea. 

I would be very unhappy I f I expereinced what you did.  If you are expereincing problems stil you may need to do 5 time 2 quarts once more .  IF he got 3 quarts in there of the wrong stuff ca 1 quart is still in there now of the bad stuff.  

I have never had that problem so I do not know what problems to expect really but I would guess harder shifting could happen due to different additives.     

 

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