Canadian Nissan Truck Club

I have always believed that the myriad of safety systems which Nissan incorporates into allowing me to shift my T-case is a vulnerability for those times when I will need 4X4 the most. The thought of knocking out a wheel speed sensor wire by a hidden branch during a water crossing and losing the ability to shift my TC just does not sit well with me. This did not happen, but ABS issues did come up about a month before I had to have a functioning 4X4 system. I designed and implemented a system which allows me to shift the TC directly on my input whenever I wished.

What I gained:
Control and a piece of mind
A certain sense of accomplishment that comes along with overcoming a challenge

What I lost:
All safety systems associated with shifting the TC – you can really mess things up if you don’t know what you are doing
Other people can’t walk up to my truck and shift the TC without my instructions
Going back to stock would be difficult
Shift on the fly – I have my own safety protocol now
Hill Descent Control – never used the feature
4WD malfunction light
What resale value?

What I did:
Took over all inputs to the TC computer and made the truck think is in 2WD at all times.
Took over the control of the 4x4 selector switch to rotate the TC motor using existing wiring and shift relays.
Took over the 4x4 cluster indicator light to tell me which mode I am in.
Took over the Hill Descent Control (HDC) switch as a safety switch.
Added my own relay/transistor logic which uses input from the four encoder lines in the shift motor assembly to control the cluster indicator as the motor is rotating

How it works:
While driving around, my 4WD selector switch is in 4HI position (I call this neutral). As long as the HDC switch is ‘OFF’ the 4WD selector does not do anything.
When I am in 2WD and want to go to 4HI or 4LO or in 4HI and want to go to 4LO – these are all Clockwise movements of the shift motor – I stop, put the truck in Neutral (I am automatic) step on the brake so that I am not moving (this is my own safety protocol – it does not need to be performed but since I took out any and all safeties I insist on it), turn ‘ON’ the HDC button, and turn the 4WD selector switch from 4HI to 4LO – the motor does it’s thing and when I am in the desired position as indicated by the 4x4 cluster light I return the 4WD selector to its 4HI (neutral) position and turn ‘OFF’ the HDC switch.
Shifting from 4LO to 4HI or 2WD or from 4HI to 2WD – these are counter clockwise movements of the shift motor – the process is basically the same except I turn the 4WD selector switch from 4HI to 2WD.

I have had this for two months now and have used it extensively. It has not let me down in any way. The circuit can be expanded for additional safety features etc. but I just wanted it done.

Here is the link to the circuit if you want to have a look under the covers…
https://drive.google.com/file/d/0B6ozDg ... sp=sharing

That some ingenuity!! Sounds like it suits your need well.

Shift on the fly and the user (wife) friendly interface are too important to me for this kind of change. I am however impressed that you've overcome the factory system and created a modern reliable means of controlling the transfer case.

X2 for what they have both said. Kudos to you JAS!

You must have been screwed once or twice to want to figure that out! Good idea, I like the idea of totally overriding everything, but man, there's gotta be an easier way.

-Does the little 4WD indicator thing on your dash still flash when its shifting and confirm when it engages?
-ABS and ABLS still work?
-Can you engage E-locker at any time?

I know the system you made works just fine but I want to throw this in there:
My abs module pooched, ABS and SLIP light always on the dash, neither are working and at least 2 wheel sensor lines are ripped. Yet I can shift the T-case and the indicator light still animates the shift... Wonder if theres a fuse or wire harness you can temporarily disconnect to bypass the 4wd lockout. As far as I know its just my ABS module that isnt working maybe its just a matter of disabling that to access 4wd in an emergency.

Wow that's something else man. Been there with a broken abs sensor more than once and I know what you mean. Kudos for you digging into this.

Pidge

Nice work, makes me really glad to have the floor shift!

Thanks for the compliments guys!

The order of events went something like this….

Had a cracked windshield replaced – crappy job – which let water in through the passenger A-pillar on torrential downpours. This got my harness wet, had 4WD issues until it dried out, then everything was OK. This was a PITA to figure out since it never happened on water crossings but it did make me question the whole system.
----then----
I swamped the truck and got more gremlins in and out of there but it did make me learn a lot about the system I was questioning already. I learned about the encoder and what it does as well as the sensors that identify the shift fork position (4LO, Wait Detection Switch, Neutral Switch). It turns out encoder signals are all that are used to do the moving and stopping the shift motor and the sensors ‘confirm’ the encoders. The cluster indicator light will flash while the shift motor is moving AND the position is not confirmed by the physical shift fork switches even though the shift motor stops where it should. All of my physical switches were bad/intermittent after the swim so I disconnected them and ran that way ever since – which means I could shift but the cluster light always flashed in 4HI and 4LO (missing the confirmation). Cheaper then replacing the switches. At this time I also had to replace my shift motor with a junkyard part so I was able to completely profile the encoder and figure out the guts of that thing. I started my schematic at that time though and got a good laugh when I looked at my Autocad drawing properties this time around.
----then----
ABS sensor issue, needed 4WD soon, and the dealer quoted me $1500 for all that they found wrong with my truck (ABS and otherwise) so I dug into it and for less than $100 solved my immediate problem.

The answer to FF’s questions:
I get the appropriate cluster indicator light when I am in a know position, but no flashing between positions.
ABS still has its issue and will fix that when the weather gets better but my hack will not impact ABS/VDC etc. I believe my particular ABS issue is a harness problem, not a sensor problem, so I will try to fix it and have ABS.
ABLS will no longer work because I am telling the truck that it is in 2WD and everything is OK.
I did an E-locker override a long time ago so that I can engage my locker when I want. Without the e-locker hack in place this TC hack would prevent you from controlling the e-locker – it is a very valid point on the ‘what you lose’ side that I did not capture.

Please keep in mind that you would only consider this if you were SOL and had no 4WD and a big $$$ estimate to fix it.

Regarding the fact that you can continue shifting even with the same set of symptoms I would only be speculating – the ABS module talks to the TC module via CAN and reverse engineering that is beyond my level of interest. I could not shift and at this point had enough of it so I wanted to solve it once and for all. Under the time constraint I got focused on a solution and that was my direction. Now that I can reflect on the schematic I see a number of improvements that could be made relatively easily but I am not going to bother. If this can help someone out or serve as a starting point for someone else to continue the effort I am happy to volunteer it.

JAS wrote:Now that I can reflect on the schematic I see a number of improvements that could be made relatively easily but I am not going to bother. If this can help someone out or serve as a starting point for someone else to continue the effort I am happy to volunteer it.

I'll call on you in a few years. My truck still has that new car smell.

It is a very impressive modification. My thumbs up to you and your ability.


Sent from my iThingy.

If you ever get SOL in the bush with a abs light not alowing you to shift. Just pull the abs fuse from under hood, Bam... It will work again.

Restarting the truck (Titan) always worked for me. Engage the transfer case before the ABS runs it's checks, once engaged it never kicked out.

New truck is manually shifted, no worries about electronics with this one.

you can also in th egen 2's do a quick reset power off the truck tap breaks 3 times turn truck back on and switch gears had to do that in my x because of a bad wheel speed sensor.