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Transmission does not drive the wheels -- what could be wrong?


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So, I took the stock engine out of 2002 996 C2 and replaced it with a custom DC electric motor. I'm still having issues trying to figure out why the automatic transmission does not spin the wheels when the DC motor is running. Mechanically, the DC motor output shaft is connected to a coupler that attaches to the flex plate and torque converter. Here is what I know so far and some things I have tried....

1) When the DC motor spins, the transmission sounds like it is spinning -- there is sound coming from the trans.

2) When I apply an RPM input to the ECU, I hear what I believe are a few solenoids that click inside the transmission.

3) When I take the car out of Park and put into D, R, or Manual, the transmission responds with a few clicks which I assume are solenoids changing states.

4) If I put into Manual and use the paddle shifters to shift up, it moves into 2nd,3rd, 4th, etc, and there are clicks from the transmission with each change. At no point do the wheels spin.

5) While in Park, if you try to manually rotate both wheels at the same time and same direction, they do not spin. If you put in Neutral, they do spin. If you put it into gear, say 1st -- if you manually spin one wheel the other spins in the opposite direction.

6) I've drained the transmission fluid and refilled and topped off with new fluid. -- No change in behavior.

7) I've fixed most ODB2 engine error codes, I'm not seeing any transmission specific codes.

a. Engine temperature now reports properly

b. Engine RPM now reports a constant 700RPM which is the idle speed of the stock gas engine as well as the new DC motor controller.

c. I've fixed 4 of the Throttle Valve input errors except P0638-- this one specifically indicates the valve is not opening the amount that is requested by the ECU. With some more time I should be able to fix this one.

8) There is still an Engine Oil level and Generator indicator lights on in the console.

To me, it seems like the output differential is not getting engaged by the trans output shaft. Is there a specific solenoid that controls this? Does anyone have a table that shows the solenoid states and which gear combinations they control?

My next step is to work through the entire Transmission Diagnostics repair manual which will hopefully help me narrow down if one of the solenoids or pressure regulators are misbehaving.

Any feedback is greatly appreciated. I'll post some pictures soon.

Thank you!

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The transmission should default to 3rd gear operation if there is a fault or it's not getting the information needed.

This is a serious question, it the electric motor turning the transmission torque convertor the proper direction and it the convertor correctly engaged into the transmission pump drive?

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My trans is the MB 722 and I did try putting it into the emergency mode per these directions - I disconnected the Tiptronic wiring harness at the connector near the trans.

post-80669-0-44612200-1346193939_thumb.p

When I turn power back on to the car, the console confirms Tiptronic is running in emergency mode. I tried both D and R, and reved the DC motor up to a couple thousand RPMs and still no rotation at the tires.

I tried this configuration a few times. No real change in behavior.

I tried to get a closer look at the shaft that drives the differential as shown in this picture.

post-80669-0-51614700-1346194500_thumb.p

I removed the plastic cover, and when in Park if I rotate the shaft by hand, the parking brake locks into place with a ca-chunk sound. If I put the car in Neutral, I can rotate this shaft and the wheels spin, wahoo! finally some progress. If I put the car into emergency mode D or R, I observed the shaft not spinning so I gave it a spin by hand and it rotated the wheels, but doesn't seem to engage the gears that are spinning from the DC motor and TQ motion.

Wvicary: Regarding your two questions, I will check the rotation - if I am looking at the open end of the torque converter, which way is it supposed to spin? And measurement depth wise, the TQ should be engaging the pump drive, but after a few more checks on my end, I may end up opening the bell housing back up to check that exact item. Stay tuned..

-K

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I believe if you're looking at the convertor face it should rotate clockwise. There is no measurement of installed torque convertor depth that I know of, I've always gone by feel as it engages the pump drive.

How are you supporting the torque convertor centering snout that normally would engage the crankshaft?

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How are you supporting the torque convertor centering snout that normally would engage the crankshaft?

These pictures show the custom aluminum part that goes between the flex plate and the DC motor shaft. Its not shown in the pictures, but the center of the coupler on the trans side had to be turned on a lathe some more to accommodate the TQ stubby snout.

post-80669-0-66861300-1346206983_thumb.p post-80669-0-53605700-1346206990_thumb.p

Rotation wise, I have it spinning the correct way, I had my hopes up that that was the issue!

Thank you for TQ install feedback, it took me a few tries to get the TQ lined up and in all the way, so I see how its possible it could have slipped off during later assembly. I think I need to pull it all apart and try again....

Once I get it off and remounted, if I put the trans in R and spin the TQ by hand can I expect the output shafts to rotate or do I need to get the RPMs high enough to start moving fluid?

Thanks,

-K

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You'd never get enough pressure/volume from the pump by turning it by hand. Be sure the torque convertor is primed as it might take up to a minute or more of idle speed RPM to fill the convertor fully especially if the pump is worn which often lead to a syphoning effect which can drain the convertor each time the engine is stopped.

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Tonight I was able to remove the engine from the transmission. I took off the TQ and put back onto the spline. I rotated until I felt it slide deeper into the bell housing. The face of the TQ is about a 1/4 to 1/2 inch deep into the bell housing and stock adapter plate. I tried using drill to spin the TQ while in drive, but it rotated the TQ too slow and the drill started to smoke, so I stopped. :oops: I bolted the DC motor back onto the TQ in a temporary position still on the floor hoist. Now when I spin the motor, I can tell its pumping ATF fluid because I'm monitoring the fill port, this is an improvement from before when fluid just kept draining out... This is good, however, if I keep the trans in emergency mode, D and R do not result in wheels spinning. I let the motor idle for a good 15 minutes and rev'ed it up a few times. Wheels never spun. What should I look into next??

Thanks for all your help thus far!

-K

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Good news - I put the car in Park today and let it idle for like 10 minutes, continuing to pump in ATF in the filler hole as much as it would swallow. I then put the car into Drive and it went into gear right away! I tested reverse and that worked too. So I am thinking the ATF pressure just wasn't present or enough?

All the previous times I was trying to get the wheels to spin, I was idling the car while in the D or R position, does the pump not pump while you are in gear if the pressure was too low to start? or is there a different latent issue that this exposes?

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You can not properly fill a Tiptronic transmission without having it be at the correct temperature.

The ATF temperature must be between 30 °C and 45 °C. An ATC inspection at an insufficient ATF temperature causes over-filling and an inspection at an excessive ATF temperature causes insufficient filling.

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Good news - I put the car in Park today and let it idle for like 10 minutes, continuing to pump in ATF in the filler hole as much as it would swallow. I then put the car into Drive and it went into gear right away! I tested reverse and that worked too. So I am thinking the ATF pressure just wasn't present or enough?

All the previous times I was trying to get the wheels to spin, I was idling the car while in the D or R position, does the pump not pump while you are in gear if the pressure was too low to start? or is there a different latent issue that this exposes?

If the torque convertor is turning the pump is pumping albeit it is a positive displacement type so more RPM equals more flow/pressure. I think you didn't have the convertor properly engaged into the pump and possibly a low fluid level condition. If it is in default mode it will require more engine RPM to engage so I recommend connecting everything you disconnected,clearing all codes and retesting.

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Good to hear.

I'll wait to hear the sound clip before I comment on the noise.

I have a question about a comment you make on your blog, you state that you're going to "hack the back-up light outputs to drive the "reverse" input on the Soliton 1." What does this mean?

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you state that you're going to "hack the back-up light outputs to drive the "reverse" input on the Soliton 1." What does this mean?

The Soliton1 is the motor controller that converts battery power to drive the DC motor based on throttle position. When driving in reverse, you typically don't need or want all the torque or RPMs that the DC motor can deliver, so there is a special input on the Soliton1 that reduces the power delivered to the motor by 50% when the reverse input is active. The input is a 0V to 12V signal active high. I tapped into the rear brake light wiring on the car and tied that wire to the input on the Soliton1. So now, when I put the shifter into reverse, the reverse tail lights light up AND the Soliton1 reduces the power delivered to the motor. This is the recommended method per the Soliton1 user guide.

-K

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I'll wait to hear the sound clip before I comment on the noise.

Here is a youtube video that is the sound of the car idling at 1100 RPMs, then rev'ing to 1500 RPMs which is where the loud noise occurs, then returning RPM down to 1100. The vehicle is in Park during the entire video.

http://www.youtube.c...bed/PkcTzYiLDBc

Edited by kurtdiver
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I've no idea what is causing that noise. Is it possible for you to view the torque convertor when the noise is occurring and see if it's vibrating? Not only must the convertor be centered but also supported via the crankshaft to some degree.

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