AA80E questions
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From: KY
AA80E questions
What gear does the transmission start out in if it has no power whatsoever? In other words if it is completely unplugged? It does move the car, both forward and backward, presumably in limp mode but I'd like to know what gear it starts in. I've not been able to find the answer in the shop literature.
Jim
Jim
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From: KY
So nobody has any clue about this huh?
I can't sy I'm really surprised, it's not that old of a transmission and I suppose it hasn't caught on for performance uses yet. Too bad. It seems to really have potential.
Jim
I can't sy I'm really surprised, it's not that old of a transmission and I suppose it hasn't caught on for performance uses yet. Too bad. It seems to really have potential.
Jim
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From: CA
I really have no idea what you're talking about. Maybe indicate what that code is? What do you mean by no power? I'm not a mechanic, but your question isn't detailed enough.
I don't think the car can start in first gear under any circumstances? Always thought it must be in park. How would it even start with no power? No battery power? No engine power? What exactly does "no power" mean? The engine will turnover and start but won't drive?
Good luck.
I don't think the car can start in first gear under any circumstances? Always thought it must be in park. How would it even start with no power? No battery power? No engine power? What exactly does "no power" mean? The engine will turnover and start but won't drive?
Good luck.
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From: KY
Thanks so much for your response. I did not mean to be unclear.
If the transmission has no electrical power whatsoever, in fact if all the connectors to it are unplugged, it will still move the car as long as the engine will run.
It will do this in Limp Home mode. I know this because I have done it. It will also reverse and move the car backwards. Doing this could possibly damage the transmission so it isn't a great idea, but it will work.
My question is, what gear does it use to move the car forward when this happens? The fault tables I've seen do not show a power failure of the transmission or transmission control module as a fault condition, and the solenoid state charts do not provide an easy answer.
I'm quite sure it isn't 1st gear. Probably not 2nd either. Beyond that I'd just be guessing, but I hope someone here actually knows the answer.
I have a second question, does anyone know how many teeth are on the input gear for the input speed sensor?
Jim
If the transmission has no electrical power whatsoever, in fact if all the connectors to it are unplugged, it will still move the car as long as the engine will run.
It will do this in Limp Home mode. I know this because I have done it. It will also reverse and move the car backwards. Doing this could possibly damage the transmission so it isn't a great idea, but it will work.
My question is, what gear does it use to move the car forward when this happens? The fault tables I've seen do not show a power failure of the transmission or transmission control module as a fault condition, and the solenoid state charts do not provide an easy answer.
I'm quite sure it isn't 1st gear. Probably not 2nd either. Beyond that I'd just be guessing, but I hope someone here actually knows the answer.
I have a second question, does anyone know how many teeth are on the input gear for the input speed sensor?
Jim
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From: CA
I'm sorry, but I personally don't know. I'm surprised the selonoids will even work to engage reverse.
You can kind of guess the gear based on engine speeds versus actual speed. Assuming X RPM at Y MPH will give an indication of gear if you look up the gear ratios.
Assuming the car isn't sensing the gear, it must default to something. Do you feel the transmission shift when you put it in drive. I assume you do, but I would think it would force first gear no matter what.
I'm no help in the second question either I'm afraid.
You can kind of guess the gear based on engine speeds versus actual speed. Assuming X RPM at Y MPH will give an indication of gear if you look up the gear ratios.
Assuming the car isn't sensing the gear, it must default to something. Do you feel the transmission shift when you put it in drive. I assume you do, but I would think it would force first gear no matter what.
I'm no help in the second question either I'm afraid.
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Thread Starter
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From: KY
I think it shifted but I'd have to take it out again to be sure. I've just been up and down the driveway. A bit cold right now to do that. Also the speedo isn't working yet which makes that method a little difficult. Maybe I could count the wheel rotations on the lift.
I know this sounds rather odd. But I'm setting up a MegaShift controller to operate the AA80E. It gets a bit involved.
Jim
I know this sounds rather odd. But I'm setting up a MegaShift controller to operate the AA80E. It gets a bit involved.
Jim
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Thread Starter
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From: KY
No, it acts just fine, about like any normal car would starting out. But 1st gear on this transmission is about 4.5:1 and I know it can't be starting out in that gear.
The thing is, I've been looking at the solenoid states for the different gears, and none of the gears really show all solenoids deactivated, so it's got me puzzled. If I knew which gear It starts out in in full unpowered limp mode It would tell me a lot about the solenoid states. That should help me decipher a little more about what goes on inside the transmission.
Jim
The thing is, I've been looking at the solenoid states for the different gears, and none of the gears really show all solenoids deactivated, so it's got me puzzled. If I knew which gear It starts out in in full unpowered limp mode It would tell me a lot about the solenoid states. That should help me decipher a little more about what goes on inside the transmission.
Jim
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From: CA
Well, I'm at my wit's end. The only other advice I can give is using a full-scan OBD reader/software, like Toyota's Techstream. It may give you position and status indicators in real time.
Although I have no idea if it would even indicate the transmission position assuming it is not connected to the ECU, although it may, who knows?
Although I have no idea if it would even indicate the transmission position assuming it is not connected to the ECU, although it may, who knows?
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From: KY
Yeah, I think it's probably time to get back in touch with my tech buddy at the Lexus shop. He sent me the tech data that I've been using, maybe he can help with the additional info.
Jim
Jim
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From: KY
Thanks Army, that helps. And that is about what the car feels like too and seems consistent with my results. That would be a 1.464 ratio and with 3.54 axle gears it feels about right in an automatic.
I'm showing that to enable 4th gear I need SL1 and SL2 solenoids engaged in order to lock up clutche-1 and clutch-4. Can you tell me how this is done? My guess is that either there is some hydraulic bypass or inversion mechanism to do that, or possibly the operation of C1 and C4 could be inverted to where they are actually on when the reference material says they are off?
I really hope you can tell me why limp works.
Thanks a bunch,
Jim
I'm showing that to enable 4th gear I need SL1 and SL2 solenoids engaged in order to lock up clutche-1 and clutch-4. Can you tell me how this is done? My guess is that either there is some hydraulic bypass or inversion mechanism to do that, or possibly the operation of C1 and C4 could be inverted to where they are actually on when the reference material says they are off?
I really hope you can tell me why limp works.
Thanks a bunch,
Jim
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From: Van Alstyne, TX
The computer tells the transmission to stay in 4th gear to minimize damage in the event of a fault code. No voltage on any of the sensors you disconnected would cause a fault code to be stored in the trans computer module which will put it in limp mode.
I know very little about the operations of a modern auto trans. if this were a 4L80E or another american made trans, I could help, but these new Lexus transmissions are complicated animals. I do know the transmission will not come out of 4th gear, so however it locks it in a gear is computer controlled, but as far as what that mechanism is I cannot say for certain. Most other auto transmissions operate by fluid pressure so my guess is it raises the pressure in that gear by engaging the solenoids in that gear only.
I know very little about the operations of a modern auto trans. if this were a 4L80E or another american made trans, I could help, but these new Lexus transmissions are complicated animals. I do know the transmission will not come out of 4th gear, so however it locks it in a gear is computer controlled, but as far as what that mechanism is I cannot say for certain. Most other auto transmissions operate by fluid pressure so my guess is it raises the pressure in that gear by engaging the solenoids in that gear only.