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Discussion Starter · #1 ·
I know this will raise some eyebrows.... No, I am not crazy... I am unable to get the parts and the repair done, it will take months to get it.
I took my RAV4 to the far south... to Patagonia. Just to get my car checked I have a one month wait. Then it comes getting the parts, doing the job, etc. I may end up without a car for many months or worse.
From what I can tell, the rear differential is busted. A heavy clunking sound comes from it, it's hard to take turns and impossible to go up steep inclines (which abound here we have mountains everywhere).
So while I get things lined up I was thinking on tinkering with the ECU to make it believe there's no differential and remove part of it so it won't engage.
In a scale of one to ten on crazy this gives eleven so no need to point out how absurd it is.
Now if somebody has an idea on how to do it, I am listening...
Thanks in advance!
 

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No need to tinker with the ECU, simply unplug the 4WD ECU. It's located in front of the glove box. The other ECU there is the TPMS so if you unplug the wrong one the low tire pressure indicator will come on.

Once the electrical connection is undone you can take off as many mechanical components such as the drive shaft until the noise goes away.
 

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Discussion Starter · #3 ·
Thank you very much Dr Dyno!!!!
Found a diagram showing where it is, posting it for reference. I have yet to take a look, but I guess there would be a single connector, just remove it and be done?
Is it possible that by removing the ECU the differential will completely disengage and no more noise would come? That would be really fantastic.
 

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... but I guess there would be a single connector, just remove it and be done? Is it possible that by removing the ECU the differential will completely disengage and no more noise would come? That would be really fantastic.
Yep, it's a signal connector. And it depends on what's causing the noise. What you're eliminating is the drive signal to the electro-coupler mounted on the front of the differential so no power is transmitted but the rear axles are still turning internal differential parts. In any case it's the first step.
 

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Well, I have to report complete success to converting to 2WD using Dr. Dyno's suggestion. Removing the 4WD ECU cable has removed the gear grinding noises (it's very easy, there's a little tab you press on the center of the connector and it slides out). I took the time to cover with painter's tape the female and male sides of the connector to prevent dust from entering.

Now I have a 2WD RAV4 that makes no noise at all. Of course the handling is different but the car is fully operational!
When this happened I stopped at the local Toyota and the chief mechanic gave the car a test drive. They couldn't take the car in and diagnose or look under the carriage to see what happened but the man drove the car and was puzzled. Never mentioned removing the 4WD ECU to disable the differential (now that I know this it's the first diagnostic action I would take, and it's very simple!). All the driving he did may have caused unnecessary damage to the gears. He said this was very weird, gave me an appointment four weeks from the day and then instructed me not to drive the car. Which in this town is a death sentence because public transportation is a disaster....

I am taking some learning from this experience:

  • If you suddenly have gear noises coming from the car's rear, you should unplug the 4WD ECU, ASAP and see what happens!
  • If your car does alright when moving on a flat surface in a straight line, then this bypass may work for you.
  • Don't stress the car in this condition. Trying to move up a hill caused a terrible noise, as the ECU instructed the 4WD to engage and it couldn't!
  • Immediately read the Rav4world forum! This place is a lifesaver!!!
Now I need to dig more into this and see what can be the root cause. The problem started all of a sudden. I diagnosed the car with Techstream and got a C1241 (low voltage) indication on the 4WD and another on the ABS/VSC/TRAC so this may have a relationship with the problem.... got my homework there!

Thanks again, Dr Dyno :smile. Great suggestion, it saved the day!
 

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Well, I have to report complete success to converting to 2WD using Dr. Dyno's suggestion. Removing the 4WD ECU cable has removed the gear grinding noises.
Thanks again, Dr Dyno :smile. Great suggestion, it saved the day!
More thoughts: Even with the coupler disengaged all the gears in the differential would be turning and likely making noise if they were damaged. So the problem may be confined to the electro-coupler itself. It's mounted on the front of the actual differential and is a separate replaceable part. Like several other member I had mine replaced for free under Toyota's "customer satisfaction" program.

I recommend resetting the error lights and seeing if they come back before trying to decipher their cause. The "low voltage" may simply be because the 4WD voltage is now zero.

And BTW, my screen has a "THANKS" button in the lower right corner. For as helpful as others have been to me sometimes I wish there was also one for "REALLY BIG THANKS."
 
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