The below info was taken from
my website:
I have the stock Multi-matic 2 speed transfer case that comes with the '99 4Runner limited. This transfer case has a push-button 4WD switch on the side of the transfer case lever that allows 4WD on dry pavement. This is great if the weather is spotty, maybe a little bit of snow in certain sections of the road. This condition can be exercised up to 62mph.
The lever can then be pulled back towards the driver, and shifted into 4-Hi. This condition is good for dirt roads, muddy roads, but should not be used on dry pavement.
The lever can then be pushed to the right, and forward and put into 4-Lo. This action will engage the transfer case into its lowest gear and lock the transfer case so it splits the power 50/50 front and rear. In stock mode, if the Grey wire mod had not been done, this is the only time you can engage the rear locker.
Since the Solid Axle Swap, I have modified the Transfer case mount. I'm using a FROR transfer case mount to hold the transfer case in position. I'm also considering making another mount to use the stock mounting location. This will give a more solid foundation for the transmission and transfercase.
Ok, how about the electronics of this beast you ask. Well, its not too bad after thinking it through and putting some relays into the mix.
First off, lets take a loot at some schematics and get a bearing on what is happening when the transfer case is moving from 2wd to 4wd.
Above are two pages to the 4wd ecu. Open these pages in different windows and reference them as we read along.
Here are the conditions and results of the transfer case:
Unfortunately, I can't have a table, so the conditions and results will be divided by basic lines.
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Condition
Transfer case lever in the H2 position, 4WD button not pushed
Result
T3 (2-4 Select switch = open)
D30 (Detection switch [shift Diff Lock = open])
A10 (ADD Indicator switch = open)
4WD = OFF
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Condition
Transfer case lever in H4F position, 4WD button pushed
Result
T3(2-4 Select switch = closed)
D30 (Detection switch [shift Diff Lock = open])
A10 (ADD Indicator switch = closed)
Full time 4WD = ON;
Can drive on pavement, Combination meter 4wd indicator - greens tires light up
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Condition
Transfer case lever in H4L, 4WD button pushed or not pushed
Results
T3(2-4 Select switch = open or closed)
D30(Detection switch [shift Diff Lock = closed])
A10 (ADD indicator switch = closed)
4WD = ON, H4 for dirt road conditions, Combination meter 4wd indicator - green tires and orange center lights are illuminated
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Condition
Transfer case lever in L4L, 4WD button pushed or not pushed T3(2-4 Select switch = open or closed)
Result
D30 (Detection switch [shift Diff Lock = closed])
A10 (ADD indicator switch = closed)
4WD = ON, maximum torque to wheels, Combination meter 4wd indicator - green tires and orange center lights are illuminated
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
And to make it even more confusing, take a good look at this scanned 4WD ECU system outline. I have put a new notes in there to try and help decipher this info:
So what does all that mean, well.....it'll help your troubleshoot what switches should be open or closed. One thing that happens in a SAS (SAC) is that the front diff is removed. This also removes the A10 (Automatic Differential Disconnect Indicator) switch, on page one. When this switch is removed, moving into 4wd doesn't work so well. Sure shifting into Low 4 works, as this is a mechanical operation with the lever. But, H4 and Full time 4WD, no deal. Not to mention, those darn lights will blink at you all day until you get this straightened out and close the loops.
What I found, was when the A10 switch (ADD indicator switch) was open, the 4WD would not work properly. The 4WD system is waiting for the ADD sleeve to slide into position, closing this switch, before it will allow the Full time or H4 4WD to work. There are a couple of vacuum actuated valves (V4 and V5, page two) that control this sleeve and thus, allow this switch to be opened and closed. When the V5 (VSV - 4WD, ADD) valve is energized, the sleeve slides into the 4WD position. When the V4 (VSV - 2WD, ADD) sleeve is energized, the sleeve slides into the 2WD position. These vacuum valves are controled via the F7 (4WD ECU). This 4WD ECU detects the 4WD button, and transfer case lever movement, and attempts to enable or disable these valves.
As you can see, a relay is needed to move the A10 (ADD indicator switch) switch to the on position when needed. However, what do you use to switch the relay on and off. Since I don't have the V5 vacuum switch any more, I used this Green wire to energize/de-energize the relay. When I swtch into 4wd, the relay is engergized and the normally open relay closes the connection of the A10 switch, or rather it grounds it out. Then the 4WD ECU thinks the front diff is ready for the 4WD, and allows the transfer case to shift into 4wd. Recall, I don't really have an A10 switch, this was removed with the front IFS diff. But, I still have the wire that comes from the 4WD ECU that is running out to the phantom switch. So, it is this wire in reality that is being left open (when the relay is not energized) and closed when the V5 switch is energized. It all works very well, and very quickly.
Hope this can guide you a little in your endeavors of fixing your 4wd.
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