NetG

I've searched and found this to be a common tranny issue with no one being able to offer a cause.

The car (92 LS400) has been running fine for the two days I've had it. All fluids are in good condition and at normal levels. I gently sprayed the engine off using my water hose (no high pressure) but uses a rag to scrub it down. Then misted off again. I had another hose spraying the undercarriage.

After that I went to drive and I could go into revers with no problems but no forward gears function.

When the tranny is in neutral and I go into d or any forward gear the rpm's go UP...when I put it back into neutral the rpms GO DOWN...odd.

no codes either

Any ideas? The water spraying underneath wasn't high pressure either...could that be the cause though?

PureDrifter

iTrader: (10)

let it dry out for a day or two and see what happens.

NetG

Just jacked up one side...the water I sprayed didn't even touch the transmission. I was spraying the very front part of the bottom of the oil pan. The tranny is bone dry right now (outside).

Now that I think of it...this might have happened once before (I've only had the car since yesterday...I have driven it over 12hr so far though)...but once I put it back into park and then back to D it worked fine and never happened again. I originally chalked it up to "Oh well a 20 year old car found the first quirk" but since it only happened once I didn't think much of it.


Do we have any transmission charts showing the valve body and fluid flow etc? Need to find the common denominator before I start probing. And are the shift linkages accessed by removing the gear selector?

Thanks again for the aid

steve2006

It's not the old broken wire on the trunk hinge harness problem is it?

NetG

would that do it? It's certainly worth my while to check, could you describe it? I've heard only one mentioning of a "notorious lexus white wire issue" but never could find more info.

I discovered just yesterday while looking for my jack I discovered what appears to be an aftermarket trailer light connector...there is no tow hitch on the car and these wires were all pulled into the trunk


NVM:

found it

https://www.clublexus.com/forums/ls4...il-lights.html

LScowboyLS

on this Aisin A341E transmission:

first, verify that the control shaft lever underneath the car is moving in unison with your gear shift position inside the car

if that looks good, unplug the main solenoid connector to the transmission, (the big plug) and you should lose your automatic shifting, but still should be able to shift to and drive in each forward gear as well as reverse, as if it were a manual transmission.

if you can't manual shift it with solenoid disconnected, then you have an internal transmission issue, and this I am afraid is not going to be a nice piece of news (big bucks and probably why the previous owner sold the car in the first place, start looking at car-part.com for your transmission with low mileage and a guarantee at a junkyard within a reasonable drive.)

I will say a prayer for ya to pass that manual shift test above, then it is just a transmission ECU type issue and not such a big deal - good luck

NetG

much thanks...is there a way to disconnect it from inside the car? Maybe further up the electrical line?

billydpowe

iTrader: (1)

why not just follow his advice?

LScowboyLS

no, it needs to be disconnected right at the transmission - the solenoid connector is kind of vertically oriented with wire bundle going upwards - located drivers side, right above rear corner of pan - it is the largest multi-pin electrical connector that connects to the solenoid area (adjacent to transmission) - you will be under there for a few minutes, because it is a bit tight in that area and you have to depress locking tab and wiggle off connector and I hope you have small but strong Japanese hands - you will need to be wearing a good headlamp and you may have to remove a small frame brace to get better access.

I would jack up driver's side at the jacking points and use something solid to insure car cannot fall, block wheels and scoot under and disconnect solenoid connector (car should be off) - then lower car and test to see if you can go through gears as a manual.

you can also back on to a set of low profile auto ramps (and have better access under there) - then push car off ramps while applying braking if test does not allow forward movement

PS - if transmission has internal issue, it is almost 100% to be failed forward clutch is the internal issue

DID YOU ALREADY:

1. Verify transmission fluid is near the top of the "COOL" range on the stick with cold engine
2. Verify the shift rod is correctly moving the control shaft lever on the transmission to each forward gear (control shaft lever is on passenger side of transmission, near passenger side of front corner of pan, the lever is maybe 3 inches long or so)

this is not odd at all, the ECU throttles up the car when you select a forward gear, this is normal.

LScowboyLS

No, it's not - if the ECU senses a grounding or voltage issue, it will disconnect the solenoid control and he wouldn't need to unplug that connector, the ECU would have already done it for him!

NetG

I can't get to the plug. I only have reverse so I can't pull up on my ramps, I backed up on them and jacked up the drivers side but I could only rub the plug with my finger tips; I couldn't see it directly, had to use a mirror. My hydraulic jack went out on me too so using just screw jacks and no forward gears makes raising the car up quit an ordeal. When I get the wiring diagrams in I will be able to trace that connector...unless the wires split off and go to different computers or they are connected to an inaccessible computer then I will simply trace them and d/c them inside the car by removing the wires from their harness, easy to do with a good pick. If for some reason that isn't possible then I'll screw jack and jack stand it up but I get more fun from working with the wires...and while the tranny doesn't work...the a/c still does :-D can't use that under the car...well unless I just want to water board myself.

There is a small heat shield that is REALLY in the way, see above for more expl. Lol my fingers are too short!!! I didn't have the car raised enough, I was hoping to find an online wiring diagram and cheat by just pulling some wires out of their connectors, and I kinda figured I'd want to check some signals at the tranny ecu anyway.

I noticed that c1 is the primary gear for transferal of power to all forward gears...that was my first guess for an internal issue. While I have not towed with the car or driven it (or any LS) for more than 3 days I can't really say 100% that it wasn't slipping. Though I do recall thinking "...only 250hp and this much weight...she moves a little quicker than I expected". It shifted smoothly, didn't stay in gear to long, downshift was good as well. It also "seemed" strong but I know how reliable butt dyno's are.

I will be surprised though if it is the clutch...I would even be surprised if it was a clogged valve body...but much much stranger things have happened. I have a backup plan though if that is the case...I didn't want to do ANYTHING to this car for a few years, not even performance related...grrr.

1. Verify transmission fluid...
Yes...I also noted it's color and odor...considering the car has had a few drain and fills (no flush) Appears as if it would be good for another couple oil changes

2. Verify the shift rod is correctly...
No and dang it! I was actually using my phone's front facing camera to see the connector, and I was even using the video record feature in case I saw a leak and wanted a better look...lol I should have left it there and hopped inside. I'll check that as well.

Ah...to me it was saying there is more resistance in the drivetrain in neutral than in forward gear...sort of a confirmation that the clutches are not offering any resistance to input of power...though it slipped my mind that auto's raise the rpm for forward gear, a/c clutch, etc...I'm so used to a manual...so it shouldn't have made me scratch my head as much as it did, thanks

I can't see this being a major mechanical failure (like tranny rebuild worthy), if I cannot find any sensor or wiring defect my next guess was the torque converter...but that doesn't fit my symptoms either. I might go ahead and do tranny d&f myself for no reason other than to look for signs of failure in the fluid and in the pan.

Oh well, I'll study the manuals when they come in. Crime novel? Mystery? Romance? No sir nothing is more of a page turner for me than a good repair manual...my mouth waters when I see wiring diagrams

I don't mind electrical repairs so long as they don't disable me!!! lol Thanks for the input, I'm getting a LOT of great ideas. Hopefully I'll have this figured out by next week after some days off with my new books

I will be so pissed if I unknowingly like...reconnect something and fix this...my '89 240sx's stock fuel system wiring was notorious for doing this to me.
"NO FUEL AGAIN!!! no power?...ok power at this connector...and this one...and this one...well wtf? It should start"...*vroom!..."well ok"...week later..."DAMMIT NO FUEL!!! ...grrr...this one ok...this one ok...seriously? you better not just"..." *vroom "SON OF A .....!!!"

NetG

update:
Unplugged the widest of the two plugs I saw. One was multiple wire (the one I unplugged). That didn't work. I also confirmed the linkage is moving.

Still broke...dammit I didn't REALLY want to do the w58 swap right now!!! LOL

perchance it's the torque converter?


I think I'm going to go ahead and drain the tranny and take a look in the pan, this will either tell me nothing...or **** tons.

NetG

Lavrishevo

iTrader: (1)

Seems odd that the transmission will go out like that. I also made the mistake of lightly pressure washing my engine. She was very unhappy for about 4 hours till everything dried out. Won't do that again.

LScowboyLS

quit GUESSING and do the procedure I outlined above, when you unplug the main solenoid connector, then the transmission will either operate correctly as a manual shift or else you still will just have reverse only, like you do now, which tells you which problem you have

1. if you can drive it as a manual shift transmission with solenoid connector unplugged, then you have an ECU or electrical problem outside of transmission

2. if you cannot manual shift into the forward gears and drive it as a manual with solenoid unplugged, then you have a failed forward clutch and need a major transmission rebuild

there are no other scenarios here, so stop worrying about the silly torque converter and other red herrings and get back to the proper troubleshooting procedure, as per Aisin & Toyota - you aren't smarter than their engineers.