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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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  • 1 month later...

There is no check engine light on so I could not get the error code. I replaced the 2 speed sensors with part number 89411-50010, with genuine Lexus parts. The problem seemed to be getting worst. At low gears, the RPM spiked up to 3000, say from 1st to 2nd, after the speed reached 20 MPH, the RPM would drops to normal. At higher speeds, say 30 to 40 MPH, the RPM is at normal levels. At every stop light, I have to turn on the hazard light to warn the drivers behind me that I am having some kind of issues. And the smell, after turning the engine off, it smell like something is burning even after a short drive around the block. Can any of you guys help? 

Little background. I had this car since there is only 19,000 miles on her. At 15,000 miles, she got the 45,000 miles service, as shown on the dealers record, which includes ATF drain and fill. In the 16 years I had her, I had the ATF drained and filled almost yearly, using only Type IV fluids from the Toyota dealers. So the chance of having a failed transmission is very remote, in my opinion. I took her to a mechanic who is specialized in transmission repair. First, he said he would drop the transmission to see if there are any shavings. But after he test drove her, he claims it is definitely the transmission and wanted to rebuild the transmission as it is the easy thing to do and get his boat payment paid for. This is the same shop that put in the 2 speed sensors for me. I handed him the 2 speed sensors and he put them in. I even had the old sensors back!

So I am asking for your help, who has this experience on a 1996 LS400, with 190,000 miles, that has the similar problem and can share your experience with me? Tomorrow I am having her towed to another shop. I already located a used transmission from JDM with only 65,000 miles on it. This is a transmission imported from Japan. I already made the reservation (the shop agree to keep the transmission until early next week.) The warranty on the transmission is 6 months. The guy who did the rebuilt on the ECM is not convinced it is the transmission issue. He said 1996 is one of the most reliable year model with the least issue on the automatic transmission. I am not sure if the shop has the experience to even tackle the solenoid issue since there are so many of them (4.) The guy who rebuilt the ECM even sent me another ECM to try to solve the issue by elimination. The only difference between the 2 ECM is that on the old one, the spiked in the RPM seemed to be happening later (at a higher gear, perhaps 2nd to 3rd) and the newer ECM the spiked is at lower gears, definitely 1st to 2nd. So he ruled out the ECM is not the culprit and I had since shipped the ECM back to him. So he suggested the speed sensors and I just completed that part. Now he suggest is one of the solenoids. I even went to the biggest Lexes dealership, with the most service bays and checked with the parts guys. But no one there seemed to know which solenoids, S1, S2, S3 or S4 is giving this issue. Or no one at that dealership knew which is the most replaced solenoids. Your input or post is most appreciated.

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Has any of the shops actually looked at the inputs that the ECU uses to control shift points?

Best I can determine, these two solenoids do the shifting.  These are the ones that you're probably interested in:

85420-50020

35270-50010

This one locks up the torque converter:

35280-50010

So far, the repair shops either seem to be scratching their heads, guessing or throwing parts at it.  It's not the preferred way to go about this, but at this point why not just replace all three solenoids?  It takes the same amount of labor to replace one as it does all of them.

Aftermarket solenoid kits with all three solenoids are less than $150 (Rostra P/N 529002).

https://www.rockauto.com/en/catalog/lexus,1996,ls400,4.0l+v8,1187513,transmission-automatic,shift+solenoid,8476

There's a 4th solenoid that controls line pressure as well - it's the one with the long "nose".

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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 board member. 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.

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A transmission shop will always want to rebuild them. Unless you have some diagnostic skills your at their mercy. At least make sure they replace the rear main seal and take them pan off to check the filter as well as the fluid in the used JDM unit.

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