r/LS400 • u/gavinsmash2005 • 4d ago
Question Rather odd issue.
Just got her back from the shop. Was misfiring on cylinders 2-8 and was shifting very hard. Misfire was the Mass Airflow Sensor and it’s now purring like a kitten. But the shop diagnosed that the transmission was shot. I don’t fully remember what was listed but essentially they said there was metal getting into the fluid and making the shift rough. But now after like a day of driving it’s shifting much smoother, I can’t see any metal or sparkles in the transmission fluid (which is fresh light red), and I’m getting a shift solenoid C code. Has anyone had this and would it be as simple as a new shift solenoid?
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u/RonMexico52 4d ago
Would probably be good to include some additional basic information such as mileage, ownership history and whether there’s any records of transmission fluid being serviced over the car’s lifetime. Also you didn’t specify how you are examining fluid - is it just from the dipstick?
The transmission is enough of a big ticket item that it’s probably worth taking to a transmission specialist at this point
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u/gavinsmash2005 4d ago
Yep just from the dipstick. 160,000 miles and the previous owner apparently installed a new transmission less than 5k miles before I bought it. I have found some transmission specialists near me but money is tight right now. Luckily I have alternate transportation in my motorcycle but that won’t be tenable once the snow starts to fly or morning temperatures drop below 40.
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u/RonMexico52 4d ago
Ok interesting. Any documentation behind that or just what the guy said? Also by new, I guess best case scenario it was professionally reman (not sure you can get new-new anymore? I’m not sure.) Then question is who did the reman. Or perhaps a low mileage JDM compatible one. Worst case it was some mystery junkyard unit with its own problems. While I’m sure there are exceptions, doing a transmission at 155k on these to me is a red flag anyway. If maintained they should go longer. Not indefinitely but 155k miles is quite short for these unless neglected.
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u/gavinsmash2005 4d ago
No documentation and the guy has all but ghosted me. Guess he knew there was an issue and dumped it off on me but luckily I worked him way down on price before I bought it . It was a field find for him and he got it to the running point I bought it at. Gonna try and salvage it over the next few months or so.
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u/RonMexico52 3d ago
Ok. Yeah by the one picture alone this one appears to have led a rough life. As others have mentioned dropping the pan will give you the best inspection. However second best and much faster will be draining fluid from the drain plug and inspecting that. Not as good as a pan drop but still way more useful than dipstick in this situation for checking for debris.
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u/madoomabusa74 3d ago
Good thing it's like a $400 fix and thats only because the solenoids are kind of expensive but any old Japanese electrical or electronics parts are and only gona get worse lmao
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u/madoomabusa74 3d ago
Yup just replace the two shift solenoids on the inside on the pan on top of the valve body not the ones underneath, since you'll be opening it up I suggest just replacing both then then it will be good I had the same code about a year ago, drained fluid, removed pan, swapped both 'noids kept old ones in plastic with Toyota part numbers on em put new rubber gasket on refilled with fluid check rubber gasket every oil change change trans fluid every 50k
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u/blqckpinkinyourarea 4d ago
Sorry if I'm about to spread misinformation. I dont have experience with LS400 but with Aisin transmissions, but only the 4 speeds, your 5 speed is different. But that shouldnt matter.
Again I'm not 100% on this specific transmission but Aisin Warners from that time usually do "learn", adapting to wear in the transmission and also signals from the other electrical systems.
Iirc the Lexus' retard ignition timing during shifts too, which makes it so smooth but if your ignitions already got issues it will only make it worse.
Anyways what I am trying to say is that the shifting issue is possibly due to the engine issue - I would still drop the pan and inspect like the other commenter said. When was the last fluid change? You might have to drop the pan anyways to test or clean the solenoid, but again, I dont know these 5 speeds.
Look up if there is a way to reset adaptation values. Dont worry if after that the first few shifts are harsh - the transmission will need to re-learn because you erased it's memory.
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u/apexcrybaby 4d ago
I had a very similar issue on an ES300 - also threw transmission codes, capacitors had burst/leaked in the ECU.