Infinity J30 transmission problem

Tiny
AL TEKHASSKI
  • MEMBER
  • 1930 INFINITI
I have a J30 1994, AT, 160,000mi. It is a car for my student kid. He was driving in a slow traffic when a sudden loss of power occurred, with gear grinding sound. Now the car starts fine, but would not move in any direction. A transmission repair shop quoted me $1500-2000 to fix it, so I decided to junk the car instead. However, before doing this, I thought it would make some sense to look at the transmission myself, for educational purposes at least. Now, here is my puzzle.

The self-diagnostics shows that there is no problem with any sensor or solenoids, and the repair manual suggests to inspect first the items related to line pressure controls. I found that the ATF was at normal level, and does not look too bad, it contains no visible metal or other particles. I don't have an oil pressure gauge, so I proceeded with "ON-VEHICLE SERVICE". After removing the control valve assembly, I found that the line pressure solenoid valve functions fine. Inside the transmission body, all accumulator pistons move freely and look fine too.

Now, the questions:
1. Is there any way to check internal valves inside the control valve body without disassembling the upper and lower bodies? Something like applying air pressure to certain holes?

2. There are three other solenoid valves: shiftA, shiftB, and overrun. They all have a resistance of 26 Ohm, but when I apply 12V to them, they do not move unlike two other valves. Are they designed to work under some bias pressure, or what?

3. Is it possible that the AT control unit, while it senses all sensors as fine, would fail to deliver actual power control signals, and needs replacement?

4. The manual suggests next to "disassemble AT" and check oil pump assembly, torque converter, and clutch assemblies. From bottom view, all mechanical parts look fine, and no signs of desintgration was found in the pan and retainer. What is the typical failure of those mechanical elements when no signs of desintegration is visible?

I would sincerely appreciate any input,

- Al

P.S. The transmission model is RE4R01A, which turns to be also in 4x4 Nissan pickups, 4x4 Pathfinders, and 300ZX non-turbo cars with VG30DE engines.
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Saturday, February 24th, 2007 AT 4:11 PM

4 Replies

Tiny
KIN CHAN
  • MEMBER
We work on 70% nissan in our shop. But never rebuild a transmission in my life.I'll try to answer ur question. If u found no metal debris. What & where u think those grinding noise came from. Now. If there is something wrong with the a/t ctrl module.U shouldn't be able to pull a code. It should be no communication.3rd. What kinda scanner u use. Did u physically get live data and watch the turbine spd and compare it from input to output. Are there any engine code. By the way. Just out of curiosity. Do u happen to teach an auto class in high school. Looking forward to hear from ur respond with all my respect for ur honorable act.
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Saturday, February 24th, 2007 AT 9:00 PM
Tiny
AL TEKHASSKI
  • MEMBER
Thanks for your reply. My clarifications follow:

That's a very good question. I was not there in the car when it happens, so I can't attest to what extend it was grinding. But so far I found no particles except normal (I guess) fine sludge around the pan magnet.

I was using the diagnostics embedded in AT controller - flashing AT light on dash board. It flashes all 11 pulses as short pulses. About the controller, I would think that the ability to communicate with lamp and ability to apply small signals to sensors and solenoids to determine whether they are shorted or opened does not exclude some failure of a power transistor that actually engages the solenoid.

The "check engine" light did never come on, so I didn't try the engine diagnistic routine. But I will try. Also, I have no live data except listening to sounds out of transmission when engine is running, and watching that free-hanging rear wheels do not move at all under any shift position.

No, I haven't been honored with teaching such a class. However, I do electrical engineering for living, and have a degree in experimental fluid dynamics. :Wink:
Thank you again for your response.
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Saturday, February 24th, 2007 AT 10:02 PM
Tiny
KIN CHAN
  • MEMBER
Heh heh heh. Takes 1 to know 1.I have a chemical engineering degree and a minor in chemistry too. But guess what I was young, crazy and stupid. Now I am a grease monkey. No no I correct this.I am a grease gorilla. Just kidding. But u sounds very scientific and I like it. Transmission is not my specialty I only know enuff to determine what area of problems and minor parts replacement. My specialty is engine performacne/driveability and emission. We use a nissan consult factory scanner but if u have acess to snap on modis, solus or mt 2500 u can see live data.I know for a fact 1 transmission expert fix all cars by scanner but u n I knew that as an engineering.A scanner only see what the computer is seeing but that is not necessary what is happening. To be safe on solenoids and switches I like to compare scanner live data with real signal by an oscilliscope.
By the way I like the way u reply very much. Very systematic, clear and methodical. U are not just an engineer for a living.I can see u have deep passion for ur work.
How am I doing? ---> Please response with followup
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Saturday, February 24th, 2007 AT 10:39 PM
Tiny
DTKNIVES
  • MEMBER
Is it too late to answer your question?
There is no gap adjustment for a Disco I, just push the sensor all the way in till it stops. Several things can cause excessive gap. Most common is loose wheel bearings, next is CV joints locking up. After that, a bent stub axle or worn stub axle bushing. Anything that causes the axle to move out of a straight plane will cause it.
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Sunday, November 4th, 2007 AT 6:16 PM

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