As a follow-up to my article on hub types I thought I'd post a few troubleshooting tips for SOTF trucks.
The original article:
http://www.planetisuzoo.com/articles.ht ... _Explained
SOTF trucks operate on the following:
1) Both CV shafts are always spinning. This means that your CV joints and boots are also always spinning which provides a nice segway to yet another article.
2) The left-side CV shaft has a vacuum or motor operated disconnect. The purpose of this is so that you aren't spinning the front differential to the point of noticeable drag to the driver. (drag as in a stiff steering wheel).
3) The transfer case also has an automatic shift mechanism for shifting between 2-high (2H) and 4-high (4H).
4) There's a computer that controls the system.
5) When you push the button the following happens:
A) The transfer case engages. For TOD trucks this just means that TOD starts doing its thing. For non-TOD SOTF trucks where's a motor on the back of the transfer case that shifts the shift-rail into 4H.
B) The computer watches for the 4WD system to become engaged (via a sensor in the t-case).
C) The computer switches two vacuum solenoids. It disables the disengage solenoid and enables the engage solenoid. If your Rodeo has the electric system it just sends power to it to engage the axle.
D) The computer watches for the front axle to become engaged (via a sensor in the SOTF actuator).
E) If anything in the chain fails, it blinks the light)
6) The Solenoid system consists of two solenoids. One colored green/blue and one colored grey. Chances are if you are having a problem with the system the solenoids are the problem. It's a good idea to exercise them periodically. (I try to do so at least once a month.) You can bypass the solenoid by moving the vacuum source directly to the engage part of the solenoid.
If you are looking for used solenoids (which you will once you price new ones), look for 2nd gen Rodeos. They have the solenoids right next to the brake-booster under the hood so you don't have to lay down in the mud at the junkyard to remove them. They will swap to a Trooper.
I've only heard of one shift-motor failure on the transfer case. That was mine. That t-case had gear lube in it at some point so that might have been the source of the problem. I could get it to engage (sometimes) by tapping the motor with a hammer. Same thing with disengaging.
If you have an electric motor on the front axle then this article might help:
http://www.planetisuzoo.com/articles.ht ... _Mechanism
It also lists the solenoids as having 42-ohms. It's interesting sure but the solenoids come as a pair from the dealer so that info might not be very useful.
For interest I removed the SOTF system on my 99 Rodeo after I got tired of futzing with the shift-motor on the t-case. To do so I
1) Replaced the transfer case with one from a 94 Trooper (automatic). This was a bolt in swap but it did require a large socket to swap the output flange from the Rodeo t-case to the Trooper t-case. I used the Rodeo shift lever because it was the right length.
2) I made the front axle permanently engaged by connecting the vacuum source from the engine directly to the lock position on the front axle solenoid. I forget which color is lock (green or grey) but I can easily check for those who care.
3) I will connect the 4wd indicator light on the dash to the 4wd switch in the t-case.
4) I will install manual-hubs. I'd have done this with the SOTF system in-tact in order to prolong the life of my CV boots, increase gas mileage (sometimes by as much as 1mph) and make the steering feel lighter.
That was a mouthful. Any Questions?
-Tad
The original article:
http://www.planetisuzoo.com/articles.ht ... _Explained
SOTF trucks operate on the following:
1) Both CV shafts are always spinning. This means that your CV joints and boots are also always spinning which provides a nice segway to yet another article.
2) The left-side CV shaft has a vacuum or motor operated disconnect. The purpose of this is so that you aren't spinning the front differential to the point of noticeable drag to the driver. (drag as in a stiff steering wheel).
3) The transfer case also has an automatic shift mechanism for shifting between 2-high (2H) and 4-high (4H).
4) There's a computer that controls the system.
5) When you push the button the following happens:
A) The transfer case engages. For TOD trucks this just means that TOD starts doing its thing. For non-TOD SOTF trucks where's a motor on the back of the transfer case that shifts the shift-rail into 4H.
B) The computer watches for the 4WD system to become engaged (via a sensor in the t-case).
C) The computer switches two vacuum solenoids. It disables the disengage solenoid and enables the engage solenoid. If your Rodeo has the electric system it just sends power to it to engage the axle.
D) The computer watches for the front axle to become engaged (via a sensor in the SOTF actuator).
E) If anything in the chain fails, it blinks the light)
6) The Solenoid system consists of two solenoids. One colored green/blue and one colored grey. Chances are if you are having a problem with the system the solenoids are the problem. It's a good idea to exercise them periodically. (I try to do so at least once a month.) You can bypass the solenoid by moving the vacuum source directly to the engage part of the solenoid.
If you are looking for used solenoids (which you will once you price new ones), look for 2nd gen Rodeos. They have the solenoids right next to the brake-booster under the hood so you don't have to lay down in the mud at the junkyard to remove them. They will swap to a Trooper.
I've only heard of one shift-motor failure on the transfer case. That was mine. That t-case had gear lube in it at some point so that might have been the source of the problem. I could get it to engage (sometimes) by tapping the motor with a hammer. Same thing with disengaging.
If you have an electric motor on the front axle then this article might help:
http://www.planetisuzoo.com/articles.ht ... _Mechanism
It also lists the solenoids as having 42-ohms. It's interesting sure but the solenoids come as a pair from the dealer so that info might not be very useful.
For interest I removed the SOTF system on my 99 Rodeo after I got tired of futzing with the shift-motor on the t-case. To do so I
1) Replaced the transfer case with one from a 94 Trooper (automatic). This was a bolt in swap but it did require a large socket to swap the output flange from the Rodeo t-case to the Trooper t-case. I used the Rodeo shift lever because it was the right length.
2) I made the front axle permanently engaged by connecting the vacuum source from the engine directly to the lock position on the front axle solenoid. I forget which color is lock (green or grey) but I can easily check for those who care.
3) I will connect the 4wd indicator light on the dash to the 4wd switch in the t-case.
4) I will install manual-hubs. I'd have done this with the SOTF system in-tact in order to prolong the life of my CV boots, increase gas mileage (sometimes by as much as 1mph) and make the steering feel lighter.
That was a mouthful. Any Questions?
-Tad