Problem #1billion

[spinn360]

Originally Posted by b3lha

Duty Solenoid C is pin c3 of the TCU (Green/Red wire). IIRC, the TCU controls the torque split by pulsing the solenoid on and off very rapidly.

My transmission is different to yours, but I have driven it with the diff lock fuse inserted and believe me when I say that you don't want your transmission locked up in this way unless you are driving on a very slippery surface. It will bind up on the slightest of bends and put tremendous strain on the differentials.

Would you rather get stuck because the road is slippy or because your transmission bound up and the differentials broke?

Well hey now our trannies are more similar. I put a fuse instead of a switch because I am only going to have the 50/50 split when it snows. And in answer to your question I would rather not get stuck in the snow.

Many people on here say if the cars in FWD all the time the diff will blow. Now you say if its in 4WD the diff will blow. Well you know what good I hope it blows!

As my car was (before I just did this) the car wouldnt even move in the snow unless I put it in 2nd and barely gave it any gas. If I wanted to change lanes it was nearly impossible to not slide. The car as I said really sucks in just FWD when its supposed to be AWD. So now when I remove the fuse the 50/50 split works. I believe either my TCU is always sending power to the solenoid making it FWD. I dont know if the TCU is bad or one of the sensors that communicates with the TCU. I have no codes on the TCU. If anyone else tells me that when the solenoid fails the car becomes FWD I would have to say you mean the TCU fails because unless your talking about the solenoid failing by sticking in the closed position it cant be true.

Also If you look at the info in LEE's PDF file it show the connectors wrong it counts from 8-1 when it should count from 1-8 as 3 in that order is an empty spot no wire. Although a few pages down it shows the voltage for that wire with the FWD fuse in with power. Not without. And normal operation were the solenoid would be making the AWD work is less voltage less power. No power equals 50/50 split 100% fluid to transfer clutch!! SO BLAH BLAH BLAH I WIN

[NikFu S.]

Originally Posted by spinn360

Many people on here say if the cars in FWD all the time the diff will blow. Now you say if its in 4WD the diff will blow. Well you know what good I hope it blows!

If an AWD car is running FWD, the front diff may blow depending on stress of wheelspin. If an AWD car is running AWD, probably not gonna blow unless the clutches are fully engaged all the time like in the event of a Sol C failure. If a FWD car is running FWD, probably not gonna blow unless too much torque is applied (+300).

Originally Posted by spinn360

As my car was (before I just did this) the car wouldnt even move in the snow unless I put it in 2nd and barely gave it any gas. If I wanted to change lanes it was nearly impossible to not slide. The car as I said really sucks in just FWD when its supposed to be AWD. So now when I remove the fuse the 50/50 split works. I believe either my TCU is always sending power to the solenoid making it FWD. I dont know if the TCU is bad or one of the sensors that communicates with the TCU. I have no codes on the TCU. If anyone else tells me that when the solenoid fails the car becomes FWD I would have to say you mean the TCU fails because unless your talking about the solenoid failing by sticking in the closed position it cant be true.

Also If you look at the info in LEE's PDF file it show the connectors wrong it counts from 8-1 when it should count from 1-8 as 3 in that order is an empty spot no wire. Although a few pages down it shows the voltage for that wire with the FWD fuse in with power. Not without. And normal operation were the solenoid would be making the AWD work is less voltage less power. No power equals 50/50 split 100% fluid to transfer clutch!! SO BLAH BLAH BLAH I WIN

You are correct. A closed Sol C engages full AWD by default, as pressure is bult onto the transfer clutch, and opens increasingly as voltage is read acting as a pressure bypass.
In the event of failure Sol C closes, the clutches are applied and over a short period of time provided the clutch packs are good, binding will deteriorate the differential, eventually breaking it, causing a FWD situation that may lead to the loss of the entire drivetrain given the right circumstances.

---
I think given the conditions you are explaining and the nonexistent history of TCU faliures either your center diff is chunking or your Sol C is sticking in a full or partly open position. It might be obstructed.

I think if you wire a switch to override the TCU and force constant 50/50 AWD you will undoubtedly blow a diff, but if you are just going to use it in slippery conditions by all means go for it.
This might be an easy way to help pinpoint the trouble.

[huck369]

You can never achieve a 50/50 split on a US 4EAT...the BEST you can get is a 60/40 split, as even completely closed the transfer clutches WILL slip some...just my thought on the matter...

[oab_au]

You are overlooking the section between the C solenoid and the transfer clutch. The C solenoid does not control the transfer clutch directly. The C solenoid controls the Pilot pressure, which operates the transfer valve, that applies line pressure to the clutch.

As you say the rear does kick in with a delayed action, binding is felt. These are the symptoms of a sticking transfer valve, not a C solenoid problem. Switching the C solenoid, won't fix the problem, as it is doing what it is suppose to. The transfer valve is not reacting to the changes in the Pilot pressure.

The rear of the trans has to come off to replace the C solenoid/transfer valve assemble, shown below.


Harvey.

[NikFu S.]

Harvey has spoken!

/thread

The pic helps a lot. I have never seen the thing and now I can put words to picture.

Now I can avoid going back and forth in my explanations of things I don't completely understand,
but I did have a feeling it was definitely a sticking something.

[oab_au]

Just to make the previous post clearer. This is the way the hydraulic pressure, to the transfer clutch is controlled.



The red line is the line pressure, that is fed to the transfer valve, and the Pilot valve. The Pilot valve regulates a constant pressure, that the C Solenoid controls, to apply a pressure (yellow) to the end of the transfer spool valve. This Pilot pressure pushes the spool valve across to allow the line pressure to flow to the transfer clutch (blue).

The C solenoid controls the Pilot pressure by bleeding it off, so that the transfer spool does not move across. This reduces the rear drive. When rear drive is needed the C solenoid shuts down, so that full Pilot pressure is fed to the spool valve to push it across against spring pressure, to allow full line pressure (red) to flow to the transfer clutch (blue).

If the C solenoid fails, full Pilot pressure is fed to the transfer valve, for 50/50 drive. The C Solenoid will post a code if it fails electrically, but most of the faults appear in the transfer valve, that tends to stick. This is due to fact that most of the driving is on highways, at speed, where the valve just sits in the 90/10 position. When the occasion arises when the valve has to move to the full transfer pressure, it sticks there to cause binding, or it does not move at all. So there is no rear wheel drive, and the front wheels just spin.

The only difference in the valve assemblies, between the US Transfer system and the Euro AWD system, is the C solenoid. The US type is a normally closed type. The Euro is a normally open type. So the signal fed to them is opposite.

Harvey.

[NikFu S.]

Originally Posted by oab_au

The only difference in the valve assemblies, between the US Transfer system and the Euro AWD system, is the C solenoid. The US type is a normally closed type. The Euro is a normally open type. So the signal fed to them is opposite.

Harvey.

That looks to be the source of a great deal of confusion.
US models default to closed awd, Euro default to open 2wd.
/memorize

[oab_au]

Originally Posted by NikFu S.

That looks to be the source of a great deal of confusion.
US models default to closed awd, Euro default to open 2wd.
/memorize

The Euro default to no limited slip clutch. In this version the clutch is not used to transmit power to the wheels. It is used as a Limited Slip clutch between front and rear wheels.

If it sticks we have binding, and if it does not work at all, we can have front or rear wheel spin. But we always have 40/60 drive.

Harvey.

[spinn360]

So your saying that even though I can get the 4wd to work when I have no power to solenoid C (because it does work when the flow is allowed I have already done the mod), that the TCU is not the prob but the UGH wait

the valve is sticking
its not the TCU
I can get it to work by replacing the valve.


DO you think that if I have the solenoid set to 50/50 for a while the valve might clear up??