A340 shifting backwards?

[a7mgte]

Right now the truck refuses to give me first gear when it's supposed to. When leaving a stop the truck starts in second gear and accelerates slowly. If I let off the gas, it jumps back down into 1st. If I step on the gas at all, it immediately goes up-shifts again. It will stay in first if I force it down manually with the shifter though. Any ideas what could cause this?

The truck is an 86 4Runner, which I've swapped in a 93 SC400 engine I got on Ebay with 38,000 original miles on it, and mated it to a 92 LS tranny, which had it's tailhousing replaced with T-case adapter from inchworm gear. The rear speed sensor was adapted from mechanical drive to electronic with the use of marlins speed sensor adapter. (which is SUPER common in junk yards on Honda Passports and Isuzu Rodeo's BTW)

The truck starts and and sounds perfect, but seriously lacks in power, and runs exceedingly hot as well despite a new three core aluminum radiator and 2300 CFM electric puller fan. (I'll lose a race up against a stock 22RE truck with 33's and stock gearing.)

I don't know if the tranny could be related to the EGR code 71 that the ECU throws, or it running hot, but I have to work on one problem at a time or this thing will never come together all the way.

 

[samsdad]

Firstly check the shifter adjustment and also the "Kick down" cable adjustment and if that is all good then it is really sounding like speed sensor number 2 is up the duff. This is the one located in the extension housing/transfer case adapter and tells the ECU what speed the transmission main shaft is turning at and thus sets the shift points. The one you are mentioning that has been converted is merely the Vehicle speed sensor which not only drives the speedo but sends a signal to the ECU, This should be a 4 pulse sensor and while some others from junk yards may look the same you need to check that you have the correct number of pulses for each revolution of the driveshaft.. What you have described is quite common when people try to use Surf or 4runner autos behind a 1UZ.

No power/running hot, back to basics, check the cam timing (belt) is correct. Most of the time they will throw an RPM code (12 or 13) but sometimes don't. EGR? could be stuck open or something aint wired up right.

 

[a7mgte]

I've checked the shift linkage, and all is good there. As for the speed sensor, it is 2 or 4 pulses per revolution if I remember right, but I did check the signal against Marlins sensor, and they are the same.

From what I understand the rear speed sensor feeds the speedometer, which in turn feeds a signal to the ECU. The primary speed sensor is still in place, and outputting a signal. Maybe one or both are weak? According to the TSRM, the ECU should shift fine with a signal from either of the two sensors though. The truck doesn't have an electronic speedo to accept the signal from the second speed sensor though, so I connected it's signal directly to the ECU. I don't have an oscilloscope so checking the pulse times, etc. are out of my reach right now.

I did expect the trans to shift at the wrong points to some degree because of the differences in the final drive ratio between the SC400 the ECU came out of and the 4Runner that it's in now. (35" tires and 5.29 axle ratio) I did use the Lexus LS400 transmission, I just changed the tail housing to accept a T-case.

My first thought was that perhaps the #1 solenoid is getting an inverted signal somehow making it shift backwards, however because it's a single solenoid and determines higher gears as well, if it were backwards then the entire shift pattern would be something like 3,4,2,1.


On the top of the motor the wiring for the EGR was never changed, as it's all still in place with the engine harness. However because the motor came from out of state, and I'm in CA, I had to get and EGR plate with the temp sensor and had to wire it up accordingly. From what I can tell there are at least three different EGR configurations for this motor. I've tried the two of them now that use a mechanical EGR, the last uses stepper motor to control the EGR. Could the error code be because the ECU doesn't see that stepper motor being that it came from a different car? ...and if I just put four 20 ohm resistors across the pins for it, so the computer thinks the motor is present, will the rest of the EGR system still work? (The ECU is CA emissions, and the motor Federal, which didn't seem the get the electronic EGR.)

...perhaps the engine side of this problem should be in another thread....

 

[gloverman]

Any transmission codes? How many pulses on the main gearbox shaft output speed sensor? The difference between 2 and 4 is double and will seriously stuff up shifting. The auto should change fine without the transfer output sensor disconnected as it is only a backup sensor if the primary sensor fails. Any chance you have wired a diagnostic plug to give you the ability to get live data? This is generally the best thing to do to solve this kind of problem. Cheers

 

[samsdad]

I have struck them where the VSS plays up or fails and they won't shift gears. If the O/D switch is wired up correctly and it's light is there you should be able to flash any transmission codes via the O/D off lamp with TE1 to E1 connected. You won't get live data unless TE2 is wired up

 

[a7mgte]

So I figured before I chase this thing any farther, I should take care of the check engine light. It turns out that my ECU was expecting the EGR stepper motor which wasn't present on my engine. So I found one and wired it up to the ECU and the check engine light is gone.

I still need to figure out how to wire up the OD light though so that I can check for transmission codes though.

The next step I took was to ensure the wiring between the tranny and ECU, which looks good. Without a good way to test though, I started by un-plugging pins one and two at the solenoid connector. These are the B-R wires which supply power to the lockup and accumulator solenoids. It didn't make any difference.

Then I unplugged the No. 2 solenoid to make sure it wouldn't be possible for the ECU to shift into 2nd or 3rd gear. With only the No 1. solenoid wired up, 1st and fourth should be the only available gears. This left me getting 1st gear only at a stop, but as soon as the truck started moving, it went directly into 4th. Which leads me to believe that I'm facing a speed sensor problem...but still doesn't explain why it downshifts back to first when I left off the accelerator.

If the ECU thinks I'm going faster than I really am, it shouldn't downshift like that. So I thought, maybe the solenoids are backwards on mine somehow and the ECU thinks it's shifting into 3rd instead of first. I moved the No. 1 wire over to the No. 2 slot in the connector. For some reason, I no longer have reverse, and when it goes into drive, the drive engagement is much more subtle.

Moving that pin shouldn't have any effect on reverse though. Reverse isn't computer controlled at all. So I unplugged the connector altogether, which should leave the tranny unable to shift at all in the "D" position since none of the solenoids are even plugged in. Oddly enough, it still shifted into drive, and reverse works again. I didn't try driving it like this at all. Sitting in the truck I can hear the accumulator solenoid charge and discharge when I move the shifter in and out of gear.

At this point, nothing is behaving at all as it is supposed to, and really has me wanting to just replace the tranny. It turns out that mine is an A30-41LE.

Anyone have an idea what I could do next before replacing this thing?

 

[a7mgte]

It actually makes sense that the truck still goes into gear with the tranny unplugged...it's just going into 4th gear. (both solenoids off)

I think I'm starting to just run through doing different things faster than I stop to think about what each of them do / don't do.

I started thinking that maybe I have a bad TPS or AFM, which is making the ECU think I'm stepping on the gas a different amount than I actually am. My engine runs with the AFM and the TPS unplugged. Albeit the engine runs almost no different when the AFM is unplugged, and does idle up quite a bit without the TPS. However I don't see any noticable difference in how it actually drives without the AFM, but does seem to have more power without the TPS...

hmmm....this sucks. So first thing tomorrow is to test the TPS, not too sure what I'm gonna do about the AFM though. That seems to be one that's not easily tested.

 

[gloverman]

Diagnosing AFM is generally pretty easy. Plug in the scan tool and check wheather the signal is changing. Also the easiest way of checking the TPS and trans signals. Cheers

 

[a7mgte]

I rigged up an LED to act as an OD light and am not getting any codes. The truck isn't tagged right now, so I'm limited to hot laps through the neighborhood until I take it to the smog referee on Tuesday. Then again, I've reset the ECU about a million times while tracking down the check engine light, so maybe it just needs more than a half mile of driving to trigger a code.

At this point, I'm think that I'm just going to give up on trying to figure out the funny shifting problem and manualize the thing to paddle shifters, skipping the ECU all together.

Still doesn't solve the truck running hot and not having any power though. Granted that it is starting a gear above what it should, the thing has no power at all even at high RPMs. From what I read from others that have done this swap into their trucks is that they are so powerfull that they are scary....Mine can be outrun by a stock 22RE truck, so something's wrong.

....alas, I should start another thread for that issue.

 

[samsdad]

If you manually shift the thing what does it do?

 

[a7mgte]

Moving the shift lever down into "L" will give me 1st only when I let off the accelerator. Otherwise it starts in 2nd and upshifts from there.

While in drive ("D") it simply skips 1st gear altogether, and wont downshift ever.

I've tried two different ECU's, same thing with both of them. So the problem is in the AFM or TPS circuit on the engine side of things, or the tranny is faulty. I would think anyway.

I think tomorrow I'll wire up a couple toggle switches to the solenoids just to verify that the tranny does function when power is applied appropriately.

I was going to wire up an arduino to record the shift signals for me, but when I thought about it more, using the arduino to handle paddle shifting seemed the better way to go...and lends itself to allowing me to create my own "automatic" mode if I want as well.

 

[samsdad]

I just re-read the whole thing and your answer is in your first post. You state that you have a 93 SC engine (and I would assume ECU as well) mated to a 92 LS auto. Well for some reason unlike the JDM models there are slight differences in the wiring so your fix may simply be changing a couple of wires around in the plug at the transmission end. I'll have a look a bit later at the wiring diagrams but in the meantime if you can send me a PM with your e-mail addy as the files even compressed are a bit big to upload here

 

[a7mgte]

I just re-read the whole thing and your answer is in your first post. You state that you have a 93 SC engine (and I would assume ECU as well) mated to a 92 LS auto. Well for some reason unlike the JDM models there are slight differences in the wiring so your fix may simply be changing a couple of wires around in the plug at the transmission end. I'll have a look a bit later at the wiring diagrams but in the meantime if you can send me a PM with your e-mail addy as the files even compressed are a bit big to upload here

I actually just gave up on getting the ECU to control the tranny, so I pulled the pins to the two primary shift solenoids from the computer and wired them to a pair of toggle switches. For the first time I have first gear while stepping on the gas.

Now I just gotta get this engine to produce the power it's supposed too.

 

[superman1722]

What did you end up finding out with this problem, have found myself in the same position in my build into my hilux