Sengr

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 just that one time?

Your input and comment is most appreciated. I am hoping to rectify this problem 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.

Sengr

Sorry the title should have been is this the shift control solenoid and speed sensor or the transmission. My bad.

timmy0tool

iTrader: (7)

have you checked the level of ATF fluid lately? also what ATF did you use after the mechanic?

it is good that you didn't do a complete fluid exchange as it most of the time causes more problems than what you want. small fluid flushes over a longer period are more ideal.

Sengr

I have owned the car for 16 years now. I have done ATF drain and fill with only genuine Toyota fluid type IV only. In my mind, I had probably done like not less than 8 fluid drain and fill, or perhaps more than that because I replace the ATF every year, at the beginning of the year since it is cheap insurance. The fluid is at the right level, as shown from the attachment. This is taken after driving 45 minutes, on level ground, with the shift at park.

Amskeptic

Sixteen years! You love your car, you know it is not feeling well, Unleashed rpms can kill clutches that are not clamping correctly, I would not mess around. Do a diagnostic code search to catch the electrical issues, do the proper hydraulic fluid pressure tests as spelled out in the manual. Your car deserves careful work.
Colin

Yamae

Your description "At lower gear, the RPM spikes up to 3500 RPM" reminds me of the lower pressure. If you don't have any error codes and you only have spikes, I would try the pressure test first. The pressure should be around 0.4MPa at idle setting the shifter D position and as you increase the rpm, it should reach to around 1.3MPa. The parking brake should be fully OK to do this test. This needs a gauge and an adapter though. The lower pressure is often caused by the clogged strainer or the clogged cooling lines. Sometimes incorrect ATF or less amount of ATF causes the problem too.

Sengr

Mr. Yamae,

What is the proposed solution here? The irregularities in the RPM happens once in a while. It happens sometimes after I travelled for some distance, like half an hours drive. Then the cars sits for like 5 minutes and I drive the car after that. So far it has happened twice in the course of several weeks. Also, in the morning, it would hesitate to move, if the car is not warmed up. If I sit there and warm up the car for several minutes, it will not hesitate to shift. I think the problem lies in the speed sensor, and one of the shift solenoid. Between these:
85420-50020 $216.57
35270-50010 $216.26
35280-50010 $329.38
which one is the most replaced solenoid. Only a high volume Lexus dealership with the most service bay would have that answer? I was hoping to gather the statistics from this board's expert service man and LS400 owner, what is the past experience on your repair history? Have you ever have to replace one of those three solenoids mentioned above? If so, which one? Your time and effort is most appreciated? I am hoping to get the right part so I don't want to send her to the junk yard as she has been very good to me over the 16 years of ownership. Nothing but reliability and good service. I know I can count on this board to provide the help and information necessary to save her. Thank you in advance.

Yamae

I would say things are not so simple. I would see the link below and think logically before jumping to conclude without comparing the symptom and the table chart. Solenoids work as a matrix in the link and a single solenoid failure causes variety of gear selection problems, you need to know.
https://www.clublexus.com/forums/ls-...ml#post9984455

Sengr

Update: I went ahead and replaced the 2 speed sensors, part number 89411-50010. The problem seemed to be persistent. The spiked in the RPM now happens at the lowest gears, from 1st to 2nd, went up to 3100 RPM. The RPM would not come down until the speed reached 25 MPH. At higher speed, the RPM is at normal levels. This happens at every stop light. And after I turn the engine off, I could smell a very distinct smell, like something is burning. Is there any tell tale sign?
The guy who rebuilt the ECM for me suggested the speed sensors first, then one of the solenoids. So I already did replace the 2 speed sensors. As Mr. Yamae suggested in his reply (see above), the solenoid issue is not that simple. I had read another post where another guy replaced all 4 solenoids from a used transmission and his transmission is working again. My question is, if I can locate a used transmission at 65,000 miles from JDM, with 6 months warranty for $450, labor is $400, why not go ahead and replace the transmission?
The guy who rebuilt the ECM further suggested it could also be the drive shaft coupler. Do you guys see that?

I am desperately looking for a direction to go. What should I do next? Tomorrow, I am having the car towed to another shop since the shop that put in the 2 speed sensors would not drop the transmission for inspection as the owner claimed that there is no power in the car. It is true though, at 1st gear, the car goes up to 3100 RPM and hardly moves. So the guy who put in the speed sensors said it is definitely the transmission. What should I tell the shop mechanic to check first? Drop the transmission, check the drive shaft coupler, check the solenoids. There is no code since the check engine light did not come on.
I managed to locate a used transmission and the parts yard agreed to hold it until early next week. By early next week I would either have to buy the transmission or have a clear path forward which I don't know what it is yet. Most shop would not work with you. They just want to rebuild your transmission as it is the lowest hanging fruit for them. They could take your money and run then. Any input or suggestion from you expert guys is mostly appreciated. I found this type of user forum is very helpful is solving the most complicated problem. I managed to save my flood damaged car back from the insurance guys and still using her. This is the big hurricane Harvey in 2017. Everybody I talked to, even the shop owners told me to get rid of my car except a few knowledgeable guys, one from Ireland, told me to buy back the car from the insurance company and fix it. I was lucky on that. All the dealer did, was to put in a new battery back (under warranty) and viola, the car came back to life and I am still driving her now. Thank you guys in advance.

Sengr

Correction:
What should I tell the shop mechanic to check first? Drop the transmission, check the drive shaft coupler, check the solenoids? There is no code since the check engine light did not come on.

Yamae

Your symptom reminds me of the insufficient ATF level issue or the line pressure is not enough. Have you checked the pressure? I would start from there. The incorrect ATF often causes the clogging problem and it blocks or disturbs the ATF flow of the cooling line. The clogged line causes the low pressure, you know.

Come to think of it, your words, "The irregularities in the RPM happens once in a while. It happens sometimes after I travelled for some distance, like half an hours drive." inform me that the problem happens when the viscosity becomes lower. The line pressure becomes lower when the viscosity is lower.

This is one of ways to clean the cooling line applying the air pressure 200kPa.

Sengr

I watched the mechanic cleaned the lines. Then I test drove the car around the block. Unfortunately, it did not solve the issue. She drive a little better but still almost the same as before. I told the shop to drop the pan and see if there is any problem with the transmission. I had since left the shop. I will call in later to check on the progress.

Sengr

At this point, it looks like the only logical path forward is to buy the JDM imported transmission for $450 and spend $400 labor to put it in. The mechanic I am working with is not willing to drop the pan and check if it is really the transmission is bad or not. I was at the shop when I watched them clean out the cooling lines according to a suggested reply by a Mr. Yamae. The shifting is a little better (at lower gear) but still pretty much the same. The RPM went up to above 3000 RPM and she moves very slowly. The mechanic kept saying it is a bad transmission. Not sure if asking him to replace the solenoid will be the viable choice. Plus, buying the 3 solenoids, would cost:

85420-50020 216.57 x2 = $433.14 (Lexuspartsnow.com said 2 required?)

35270-50010 = $216.26

35280-50010 = $329.38 making a subtotal of $978.78

say labor of $200 (just a guess) making a grand total of $1178.78

I am definitely doing the used JDM transmission with 65,000 miles. I think the mechanic is asking me to pick that path too. I sincerely thank you all for contributing your time and trying to help me to resolve the issue. I know, I want to go to replace the solenoid route but I am just an ordinary civil engineer without much handy skills. This would be an easy way out, plus, I am kind of tired to deal with the research and running around... Cheers!