95 X auto 4wd????

[94ZebraRanger]

I have searched and gone though all the info but haven't really given me the answer.
I am looking to get an 95 Explorer xlt with the 2wd/auto 4x4, 4x4 low. I am planing on off roadin with it. I would like to beable to put it in 4x4 Hi instead of auto.

From what I have read in the posts.

95-96 have full time front axle
they have vacuum switches for 4wd on the axle that engage the 4wd.

questions are as follows:
does the T/C opeate all the time sending power to the front and only engaging when the need arises?
does anyone know what accually tells the T/C & front end to engage what slippage happens?

What happens when 4 LO is engaged. What turns on??


There MUST be away aside from going to the extreme and changing out the front axle for a straight and a T/C swap.

Tim

 

[Doug]

As far as i know there is no way to get 4hi out of one of those t-cases. The way the auto 4wd works is there is a clutch going to the front axle and then the computer detects the rear wheels slipping it engages the Torque On Demand Clutch. When you put it in 4lo that clutch locks.

 

[Bshmastr]

Check out Dead Link Removed where we talk about hacking the 4wd system with relays that interrupt the computer's signal. Pay special attention to the last two pages where Jason_25, Jefe, and I are discussing how to use a relay and 12v to lock the electromagnetic clutch which drives the front end.

It really came down to the fact that no one knew the correct voltage to apply to that clutch. The wiring was the easy part, but someone needs to use a multimeter to figure out what voltage the computer outputs when it engages the front driveshaft, and then duplicate that. That involves taking the seat out, pulling up carpet, and cutting wires, which Jason has done, but I don't believe he had a multimeter to test it while he was there. He was more interested in getting 2wd low than 4wd high.

 

[dogfriend]

Originally posted by Bshmastr
. Pay special attention to the last two pages where Jason_25, Jefe, and I are discussing how to use a relay and 12v to lock the electromagnetic clutch which drives the front end.

It really came down to the fact that no one knew the correct voltage to apply to that clutch. The wiring was the easy part, but someone needs to use a multimeter to figure out what voltage the computer outputs when it engages the front driveshaft, and then duplicate that. That involves taking the seat out, pulling up carpet, and cutting wires, which Jason has done, but I don't believe he had a multimeter to test it while he was there. He was more interested in getting 2wd low than 4wd high.

I read the original patent on the Control Trac system and the explanation given in the factory manual. They indicate that the GEM sends a modulated signal to the transfer case clutch in 4wd Auto and I'm pretty sure it does in 4wd Hi except that the duty cycle is higher. I think it only locks the clutch in 4wd Lo (and shifts into low range).

If you apply a constant signal to the clutch in Hi range, I don't think you will get the same result as the stock 4wd Hi. This might actually be better for hardcore off road but could be risky for driveline wind up at faster speeds.

 

[dogfriend]

Originally posted by 94ZebraRanger

does anyone know what accually tells the T/C & front end to engage what slippage happens?



Tim

Yes, there are two Hall Effect sensors on the front and rear driveshaft. There is a ring on each driveshaft inside the transfer case that is read by the two sensors. When the GEM (computer) determines that that one of the driveshafts is turning faster (slipping) it begins to engage the clutch to provide more torque to the front axle in steps of 8%. It continues to ramp up until it detects that slipping is no longer occuring, then ramps back down. In 4wd Auto it is always sending a small amount of torque to front axle. The 95 - 96 models have vacuum disconnect for 2wd, 97 + are always in 4wd Auto.

 

[94ZebraRanger]

Is the front axle locked all the time or????
thanks for the info

Tim

 

[dogfriend]

Originally posted by 94ZebraRanger
Is the front axle locked all the time or????
thanks for the info

Tim

I'm not quite sure what youre asking. The front diff is an open diff.

For 95 -96 there is a vacuum disconnect at the front axle. I'm not sure of the details of the operation because my manual is for 97. From reading the patent info, I believe that the GEM also disables the electronic clutch in the transfer case whenever the vacuum disconnect is disengaged at the front axle.

For 97+ there is no vacuum disconnect, the front driveshaft is always turning. The electronic clutch is turned on using a PWM (pulse width modulated) signal. A low amount of current is sent at all times, the current is stepped up by increasing the amount of "on" time of the PWM signal whenever slipping is detected.

The patent says that in 4wd Lo, the GEM goes into a loop to ramp the signal to maximum, but it is still a PWM signal not a DC signal.